- Posted by Okechukwu Anosike on October 3, 2011
- [Permalink]
As a process engineer designing a process plant, coming up with the best possible design option for a process is paramount. One has to ensure that all important process parameters and specifications are taken into account adequately, be it plant capacity, product purity, safety concerns, plant control stability, or of recent significance, energy efficiency and reduced emissions. The more adventurous designers propose novel solutions and designs to meet process challenges, while the more seasoned designers rely on tried and trusted process configurations with minimal tweaks.
Principles like heat integration and process intensification have acquired wide acceptance as means of reducing energy consumption and capital costs respectively to meet process requirements. Many other innovative approaches are used to the meet challenges facing different processes; however, the viability of all of these is determined by one single criteria – what is the economic benefit?
Early in the career of every process engineer, or even before graduating from university, there comes the realisation that the elegance or innovation of any process design is secondary to the economic bottom-line. In fact, irrespective of the process, the engineering challenge invariably becomes designing a plant to meet real budgetary constraints. Whether one is designing a large integrated refinery or a small chemical plant, the plant would eventually get built based on how the design performs economically. It is therefore, very important for a process designer to get a handle on process economics at the onset.
Process economics is determined by the decisions made by the process designer early – in the feasibility and Front End Engineering Design (FEED) stages. About 80% of investment decisions are made in these stages, as a preferred process route is selected based on its performance in regards to critical process parameters, within an identified cost constraint. The selected process route is then designed in detail, before it is sent to a cost estimator to produce an estimate and a budget for a project to build the plant. Invariable some of the decisions made earlier bring the process designer in conflict with the cost estimator. Any subsequent change in plant design resulting from these conflicts end up costing a lot more than they would have if they had been originally incorporated in the design.
Over the past two decades, process simulators have become the most important tool for process design. Popular commercial packages like AspenTech’s Aspen HYSYS and Aspen Plus, Honeywell’s UNISIM, SimSci’s PRO/II, PSE’s gPROMS and the like, are essential companions that give designers the ability to quickly test out their designs. As long as the appropriate property method like an equation of state (such as Peng Robinson or SRK), an activity coefficient model (such as NRTL or UNIQUAC) is used in simulating the process, then the results acquired are adequate for high level decision making. Designers can now simulate a large number of process routes and compare important process parameters to select the best process design option.
An additional tool that would help process designers make better choices is a process economic performance comparison. Most serious design companies incorporate this in their design processes, but it is usually cumbersome, involving the use of generalised estimates and indices, along with unrealistic assumptions. As a result, the reliability of such an exercise is undermined. Consequently, AspenTech introduced Aspen Process Economic Analyzer (APEA, formerly Icarus Process Evaluator – IPE), an important innovation that gives process designers the avenue, in addition to process parameters, to rapidly determine economic parameters reliably. Common financial indices such as Net Present Value, Internal Rate of Return, Profitability Index, Pay Back Period, and so on can be easily compared and used to choose the best process design.
APEA is designed based on AspenTech’s Icarus technology, a cost estimation tool. Aspen Icarus is a widely used tool that supports the generation of conceptual and detailed cost estimates and schedules over a project life cycle. It creates accurate budgets from conceptual definitions, and offers powerful tools to optimize control, power, and piping as well as supports project relocation and scaling based on plant size. It has been field-tested in about 50 countries and over 1,800 locations all over the world. It has an industry track record of proven performance for over 30 years.
Aspen Icarus works by simulating the fabrication of a process item from the bottom up, avoiding the use of factors, and then using current industry cost data of material and labour costs to generate an accurate cost estimate for the item. Installation bulks are also generated for every project component. Other project costs like indirect costs are also given proper consideration, accounted for through industry best practices. The calculation engine also uses engineering design codes, a detailed material database, standard fabrication methods, proven proprietary equipment cost models, a critical path method schedule, defined contractor and engineering to produce accurate estimates.
APEA has an interface with most commercial process simulators, and a particularly seamless integration for the AspenTech simulators. So process engineers are now able to send the simulation files of their process routes as inputs to APEA, and capital and operating costs are determined in addition to all kinds of economic parameters. This means that better choices can be made quickly, resulting in reduction in waste, engineering man hours, project conflicts, and improving the possibility that the plant is built.
Although this tool has been available for about a decade, it has only recently gained wide acceptance by process engineers, who traditionally avoid dealing with cost aspect of their designs. Therefore, in addition to the process simulators, a process cost comparison tool should be a must-have for all process designers.
Reference: Chechet Biliyok
Tags:
Category: Chemical Engineering, Process Engineering
Actions:
E-mail | Comments (84)
Share With: Twitter | FaceBook