Achieve Model Operations

Plants can solve a range of problems by leveraging design models

By Rob Hockley and Ron Beck

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Fluor, which calls such integration “cost optimized design,” cites a number of benefits [2]. These include the ability to focus on technology/cost trade-offs early, improved quality of estimates and better cost awareness during design.

BASF estimates it saves 10% to 30% in capital costs 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].

 

Figure 2. New uses of design models in operations require changed workflow.

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 models within the plant operating environment can provide even more benefits.Moving models from R&D/engineering into plant operations.

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

The use of models in plant operations
Type of model
Used for
Description
Traditional process simulations
Troubleshooting, debottlenecking, process revamps
Used by plant-based engineers on an “as required”basis to support plant operations
Off-line process models
Supporting operational decisions, advising operations, reconciling plant mass balances, calculating product properties, training process staff
Used daily, weekly or whenever needed

Typically have a customized user interface in Excel or Visual Basic

May link to some real-time data

Initiated by a person

 

Real-time open-loop models
Calculating and advising on optimal plant operating conditions to maximize financial performance

Typically used each shift, daily

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