Excel-simulator interface

The BIOCHLOR Natural Attenuation Model simulates chlorinated solvent natural attenuation using an Excel based interface. BIOCHLOR simulates the following reductive dechlorination process ... 

By far the most common methods of studying aqueous interfaces by simulations are the Metropolis Monte Carlo (MC) technique and the classical molecular dynamics (MD) techniques. They will not be described here in detail, because several excellent textbooks and proceedings volumes (e.g., [2-8]) on the subject are available. In brief, the stochastic MC technique generates microscopic configurations of the system in the canonical (NYT) ensemble the deterministic MD method solves Newton s equations of motion and generates a time-correlated sequence of configurations in the microcanonical (NVE) ensemble. Structural and thermodynamic properties are accessible by both methods the MD method provides additional information about the microscopic dynamics of the system. 

The microscopic structure of water at the solution/metal interface has been the focus of a large body of literature, and excellent reviews have been published summarizing the extensive knowledge gained from experiments, statistical mechanical theories of varied sophistication, and Monte Carlo and molecular dynamics computer simulations. To keep this chapter to a reasonable size, we limit ourselves to a brief summary of the main results and to a sample of the type of information that can be gained from computer simulations. 

The main goal of the molecular dynamics computer simulation of ionic solvation and adsorption on a metal surface has been to test the above model and to provide more quantitative information about the different factors that influence the structure of hydrated ions at the interface. Unfortunately, most of the experimental information about these issues has been obtained from indirect measurements such as capacity and current-potential plots, although in recent years in situ experimental techniques have begun to provide an accurate test of the above model. For a recent review of experimental techniques and the theory of ionic adsorption at the water/metal interface, see the excellent paper by Philpott. ... 

Two excellent examples of this membrane system have been developed, NS-lOO and PA-300 (5,15). The NS-lOO membrane was made by impregnating a polysulfone support with a 0.67 percent aqueous solution of polyethylenlmine, draining away excess reagent, then contacting the film with a 0.1 percent solution of toluenediisocyanate in hexane. An ultrathln polyurea barrier layer formed at the interface. This membrane was then heat-cured at 110°C. A later version of this membrane was developed (designated NS-101), which used isophthaloyl chloride in place of toluenedilsocyanate, producing a polyamide (16). With either type of membrane, salt rejections in simulated seawater tests at 1000 psi exceeded 99 percent. 

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... 

In all simulations of clay mineral systems we apply periodic boundary conditions at constant pressure and temperature (constant NPT), This allows the system volume to change freely at 100 kPa (1 bar) external pressure and 298 K. Furthermore we employ Ewald summation to compute both electrostatic potentials and dispersive van der Waals interactions, and the simulations are fully dynamic, using the Discover module and Insight II graphical user interface of the MSI molecular modeling suite (MSI, 1997). The free energy perturbation technique is not implemented in this software per se so that many of the aforementioned calculations have to be performed with spreadsheet software (e.g., Microsoft Excel). 

Conformational equilibria [249, 264], electron [217, 265], ion [200, 266, 267], and molecule transfer [268] across liquid/liquid interfaces consisting of water and an organic solvent have recently been studied by several authors. Also, the aqueous/ liquid mercury interface has been investigated (see above and Ref 78, 81). Much of this work has been reviewed recently in two excellent papers by Benjamin [251, 269]. Here, I would like to state that simulations of liquid/liquid interfaces are likely to become increasingly important, for several reasons ... 

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. 

Interfacing between a process simulator and Excel (containing an optimization... 

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. 

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

To illustrate the interfacing between Aspen HYSYS and Excel, an ammonia synthesis process (Figure 4.C.1) is taken from simulation examples available in Aspen HYSYS. This process consists of several reactors, separators and heat exchangers/coolers. The main steps of this interfacing are shown below. Some familiarity with Aspen HYSYS, Excel and VBA is required for adopting/using them. Note that sample Aspen HYSYS and Excel files for interfacing can be downloaded from this book s website. 

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