Chemical Processing - June 2008 - (Page 20)

integrated process engineering workflow Figure 1. Process models can play an important role in all four phases. Conceptual design/r&d Analyze for safety & control Model key equipment Process performance modeling & analysis Analyze economic performance Basic engineering Develop basic design package Analyze detailed costs Detailed engineering Develop detailed plant design Operations/ maintenance Reuse process model for operations decision Reuse process models for planning decisions and up to $2 million/yr. in energy through its i-TCM (intelligent Total Cost Minimization) project approach, which involves performing process simulation, cost analysis and equipment modeling in parallel [3]. The goal is to optimize capacity, reduce operating costs and develop better designs for new or revamped plants. Design/operability workflow. The use of dynamic models for safety and operability analysis is another advance. This clarifies whether a design simulation solution is stable under real-world dynamic conditions. The goal is to use the same unit operations models for both steady-state and dynamic analysis, avoiding having to develop the models again. Shell Chemicals takes this approach to model reactor and relief systems to ensure that designed safety systems will be able to contain any runaway reactions. This application of dynamic modeling improves operations safety and reliability and saves operating costs through optimized normal operations [4]. Conceptual/basic/detailed engineering workflow. Integrated basic engineering represents another area where workflows have advanced. The heat and material balance and flow sheets from simulation studies are directly input into the basic engineering process, where multiple disciplines define the FEED and then pass that information to detailed design. WorleyParsons, by linking together process simulation, basic engineering and detailed design, achieves an estimated 25% increase in engineering efficiency and 50% reduction in time for basic engineering [5]. Moving models from R&D/engineering into plant operations. Models developed during process development and design phases of a plant represent significant engineering effort and knowledge. The design benefits include engineering productivity and reduced capital expenditure/plant lifecycle costs. Re-using those same JUNE 2008 chEmicalprocEssiNg.com 20 models within the plant operating environment can provide even more benefits. Process models suitable for use in plant operations span a spectrum from off-line steady-state simulation to debottlenecking analysis through to closed-loop real-time optimization of process performance. Table 1 highlights the different levels of benefit and implementation time and effort. Figure 2 illustrates the typical workflow in taking design models into operations. Making the transition Off-line process models represent the first step in reusing design models in a more automated or convenient way. Because they serve an individual plant or operating unit, their topology is fixed and the range of operating conditions is well understood. The models are used for specific calculations such as for: • advising on operating set points for individual equipment items; • achieving a reconciled plant mass balance; • determining product properties; • analyzing energy usage; • comparing actual versus design performance; • responding to changing market conditions; • meeting product specifications; and • retaining and enhancing process knowledge. Even though they may connect to real-time data systems, off-line models aren’t fully automated; a person normally initiates runs. Models produced during the design phase usually require additional work before they can be used as off-line process models. After all, in design the simulation is created and run by an experienced engineer, who understands the constraints of the model and the range of valid conditions. If difficulties such as convergence failure occur, the design http://chemicalprocessing.com

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Chemical Processing - June 2008 Contents From the Editor ChemicalProcessing.com Field Notes In Process Energy Saver Compliance Advisor Achieve Model Operations Bolster Your Condition Monitoring Toolbox Particle Analysis Makes Solid Progress Improve Batch Reactor Temperature Control Improve Your Job Security Plant InSites Process Puzzler Equipment & Services Product Spotlight/Classifieds Ad Index End Point

Chemical Processing - June 2008

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