Excel-Aspen Plus interface

Based on the example in Section 4.6, simulate one- and three-stage natural gas separation processes in Aspen Plus. Interface the Aspen Plus simulation file with the Excel-based optimization program, and then optimize the natural gas separation for single and/or multiple objectives. 

Floudas, C.A. (2000) Deterministic Global Optimization - Theory, Methods and Applications, Kluwer Academic Publishers, DordrechtFontalvo, J. (2014) Using user models in MATLAB within the aspen plus interface with an excel link. Ingenieria EInvestigacion, 34 (2), 39-43. 

These models are largely agreed upon by experts in the whole world. Customized and own models / equations may be entered by the Aspen Plus interface to integrate Excel code as well as old Fortran algorithms. 

The Aspen Properties implementation of the NRLT-SAC method is available as a template. aprbkp file to license holders of Aspen Properties or Aspen Plus release 12.1 or above, by contacting Aspen s support centre or regional sales offices. The template is distributed with an Excel interface to simplify the data regression process and is suitable for non-expert users of Aspen Properties. Numerous Excel templates are available for data analysis and design calculations, based on the NRTL-SAC model. 

Simulators like HYSYS and ASPEN Plus can be interfaced with Microsoft Excel or Visual Basic because of their ActiveX compliance. This feature can be used to optimize the process modeled in such simulators using powerful optimization algorithms written in high-level... 

Global SOO and MOO optimization methods, particularly recent ones, have been implemented and are readily available in Excel, MATLAB, C-i-i-, FORTRAN, and so on (Table 4.1). But, they may not be available in process simulators. So, interfacing between a process simulator (for example. Aspen HYSYS, Aspen Plus or ACM) and a global optimization program (for example, I-MODE in Excel) is necessary for improving the design of chemical processes. In particular, students and practitioners are familiar with Excel, and can easily use worksheets in Excel for computations, data analysis, plotting, and so on. 

In natural gas, methane is the main component, and other hydrocarbons such as ethane, propane and butane may be present in smaller quantities. Water, H2S and CO2 are also present as impurities in natural gas, and they have to be removed before pumping the natural gas through pipelines. An amine absorption process is commonly used for removing these impurities. Nowadays, membranes are being explored for natural gas processing (Baker and Lokhandwala, 2008 Ahmad et al, 2012 Niu and Rangaiah, 2014). This section presents simulation and optimization of such a membrane separation process for two objectives, using Aspen Plus, ACM, I-MODE and interface between Aspen Plus and Excel. As mentioned earlier, chemical processes can be simulated in Aspen Plus. In Section 4.3, a membrane model has been implemented in ACM, which can be added to Aspen Plus. 

The I-MODE program of Sharma and Rangaiah (2013b) has been used to optimize the gas separation process for two objectives. It has taboo list, termination criterion and selfadaptation of algorithm parameters. In this study, a taboo radius of 0.01 and population size of 100 are used, and search is terminated based on the maximum number of generations (MNG = 100). The I-MODE program in Excel is interfaced with Aspen Plus via VBA (Section 4.5). 

Appendix 4B Interfacing of Aspen Plus v8.4 with Excel 2013... 

Figure 4.B.2 VBA code for interfacing Aspen Plus file (for simulating the separation process in Figure 4.B.1) with Excel.

Simulate the separation of acetone, methanol and toluene process (Figure 4.B.1 in Appendix 4B) in Aspen Plus. Identify important objectives, decision variables and constraints for this separation process. Interface the simulation file with the optimization program (in Excel or MATLAB), and then optimize the separation process. 

---