Integration of simulation tools

The integration of simulation tools is necessary to cope with the variety of needs in process engineering. It is desirable to open the access to simulation technology to a larger number of model suppliers. This can be realised by a cooperative approach between the community of users and of software producers. The availability of simulation systems on Internet can boost the use of simulation technology in a global environment. 

S. Tanev et al., Advances in the development of simulation tools for integrated optics devices FDTD, BPM, and mode-solving techniques, Proc. SPIE 4277, 1-20 (2001). 

The basic goal is to provide an environment for the integration of simulations and advanced process conttol tools. The technical and semantic integration is based on... 

The multimedia model present in the 2 FUN tool was developed based on an extensive comparison and evaluation of some of the previously discussed multimedia models, such as CalTOX, Simplebox, XtraFOOD, etc. The multimedia model comprises several environmental modules, i.e. air, fresh water, soil/ground water, several crops and animal (cow and milk). It is used to simulate chemical distribution in the environmental modules, taking into account the manifold links between them. The PBPK models were developed to simulate the body burden of toxic chemicals throughout the entire human lifespan, integrating the evolution of the physiology and anatomy from childhood to advanced age. That model is based on a detailed description of the body anatomy and includes a substantial number of tissue compartments to enable detailed analysis of toxicokinetics for diverse chemicals that induce multiple effects in different target tissues. The key input parameters used in both models were given in the form of probability density function (PDF) to allow for the exhaustive probabilistic analysis and sensitivity analysis in terms of simulation outcomes [71]. 

In spite of the potential benefit, the possibilities of logistics simulation are often not fully exploited. Some reasons are a lack of knowledge about the basic metbod-ology and the available simulation tools, the fact that simulation models are rarely deployed more than once, and simulation investigations are often integrated into the planning process too late. 

The way of using the index is flexible. Comparisons can be made at the level of process, subprocess, subsystem, or considering only part of the factors (e.g. only process oriented factors). Different process alternatives can be compared with each other on the basis of the ISI. Also the designs of process sections can be compared in terms of their indices in order to find the most vulnerable point in the design. Sometimes a comparison based on only one or two criteria is interesting. E.g. a toxicity hazard study can be done by considering only the toxic exposure subindex. Because its flexibility the total inherent safety index is quite easily integrated to simulation and optimization tools. 

For a more detailed analysis of measured transport restrictions and reaction kinetics, a more complex reactor simulation tool developed at Haldor Topsoe was used. The model used for sulphuric acid catalyst assumes plug flow and integrates differential mass and heat balances through the reactor length [16], The bulk effectiveness factor for the catalyst pellets is determined by solution of differential equations for catalytic reaction coupled with mass and heat transport through the porous catalyst pellet and with a film model for external transport restrictions. The model was used both for optimization of particle size and development of intrinsic rate expressions. Even more complex models including radial profiles or dynamic terms may also be used when appropriate. 

Digital simulation is a powerful tool for solving the equations describing chemical engineering systems. The principal difficulties are two (1) solution of simultaneous nonlinear algebraic equations (usually done by some iterative method), and (2) numerical integration of ordinary differential equations (using discrete finite-difference equations to approximate continuous differential equations). 

The Feynman path integral formalism " in quantum mechanics has proven to be an important vehicle for studying the quantum properties of condensed matter, both conceptually and in computational studies. Various classical-like concepts may be more easily introduced and, in the case of equilibrium properties, the formalism provides apowerful computer simulation tool. 

Since its introduction in 1971, SPICE (Simulation Program with Integrated Circuit Emphasis) has become the most popular analog simulation tool in use today. In the last 15 years, we have seen explosive growth in the use of SPICE, with the addition of Berkeley SPICE 3 enhancements, and support for C code model and mixed-mode simulation using XSPICE (Cox et al. 1992, Kielkowski 1994).We have also seen many new companies emerge as developers of SPICE-based simulation tools, most of which are currently available for the PC platform. 

With the introduction of advanced process simulation tools [25], the so-called integrated process development established. Here the most time-consuming pilot plant phase is bypassed by a combined approach of experimental miniplant testing and numerical process modeling. 

The principle of integral process development [26] covers much more than just the optimization of a process. This approach begins with computer-aided decision procedures in the conception phase. Tools are available in which the process structure is suggested, for example should the process be a batch or a continuous operation The software tool for process synthesis PROSYN uses databases which include knowledge of experts, material data and calculation models for unit operations. Interfaces to process simulation tools such as ASPENPLUS and material databases are also supplied. PROSYN also delivers an economic evaluation of the future production process. 

The above-mentioned integrated process development combines simulation tools with miniplant equipment to bypass the set-up of a pilot-scale plant Similar to this combined approach, a micro structured reactor plant can bridge laboratory-scale and micro-scale development. One could think of a future micro-integrated process... 

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