Environment and control issues in design

The basic principles guiding the operation of the processing units of a che mical process are based on the following objectives. Safe operation of the processing units. Specified production rates must be maintained. Product qu ality specifications must be maintained. Perform satisfactorily under condi tions different from the nominal design conditions. While process design ai ds in performing the principal function of the industry. that is to convert raw materials into products, it is process control and operability that is responsible for satisfying the above objectives. Currently, the most strik ing flaw in any industrial operation is the lack of associative interaction between the design and control systems. An improper interaction between th e two not only leads to a design which might be uncontrollable, and hence i nfeasible, but also incurs a lot of expenses while attempting to operate in the uncontrollable regions. This research mainly focuses on analyzing the importance of the interaction between design, controllability and operabili ty issues. A qualitative and a quantitative analysis of the criterion for o perability that could be used during the design phase of a process have als o been performed. Then these criteria have been tested on several test proc esses. Controllability has been assessed by the method of singular value an alysis (SVA), which helps in the design of different control strategies, an d compare them with a controllability index called condition number. Operab ility is assessed by the economic feasibility, environmental impact, safety , resiliency (ability to tolerate and to recover from undesirable changes a nd upsets) and flexibility (ability to operate at a range of feed condition s and parameter variations) of the process design. Quantitative measures we re developed for economic feasibility (by annual equivalent profit) and env ironmental impact (environmental impact index). The operability and control lability analysis has been incorporated into the design of the process. Whi le the qualitative analysis gave a feel of all the issues that need to be c onsidered to make a process operable, the quantification of the criterion g ave a simple method by which the best operable and controllable alternative can be chosen. Thus, with the above analysis, a procedure to assess the op erability and controllability of a process was developed and the importance of their integration with design was proved. This analysis will be describ ed within a framework that evaluates and optimizes processing alternatives where economics, environmental impact, and controllability are considered. (C) 2000 Elsevier Science Ltd. All rights reserved.