Simulation issues

The simple single column considered in Chapter 2 had no recycle streams since there was only a single unit. In this extractive distillation column, the design of the first column depends on the bottoms from the second column. Therefore, we must worry about converging this recycle loop. 

00275 kmol/h of DMSO impurity in the distillate of the extractive column and 3.64 X 10 kmol/h of DMSO in the distillate of the solvent recovery column. So we specify a makeup flow rate of 0.00275 kmol/h. 

Converging the recycle in this system is easy. In general, this will not be true. The heterogeneous azeotropic system studied in the next section illustrates some of these difficulties. A more robust method for converging recycle will be discussed. 

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C. Packed Bed CFD Simulation Issues 1. Packed Bed Flow Regimes... 

Simultaneously to the 3D simulation issues another team consisting of the separation expert, compounding expert and simulation expert is working on the degassing concept validation. Therefore an integrated overall CHEOPS simulation is prepared and executed to quantify the degassing capacities of every single system component. This is described in Subsect. 5.3.5. 

Gunter. B. 2002. Enhanced coalbed methane recovery and CO2 storage simulation issues and model comparisons. Present status and perspective of CO2 sequestration in coal seam Proc. Intern. Workshop, Tokyo, 5-6 September 2002. JCOSC JCOAL. 

Robinson, S. Conceptual modeling for simulation issues and research requirements. In Proceedings of the 38th conference on Winter simulation, pages 792-800, 2006. 

Ultimately, chemical engineering methods and technology are needed to transform this molecular and empirical chemistry into a real process. This chemistry must be understood in terms of many scale-up, design and simulation issues that will influence the economics of the process. For example, process equipment and operating procedures in supercritical fluids require special attention to safety issues because of the high pressures involved. There is an economic penalty in achieving the compression required to reach operating pressures and to recover products at ambient conditions. Sometimes extensive pretreatment of feeds is required or a specialized co-solvent may have to be added. 

The stream conditions shown in Figure 14.1 are from the dynamic simulation of the process at steady-state conditions with the recycle of solvent loop closed. This loop did not converge in the steady-state Aspen Plus simulation. Other simulation issues are discussed in the next section. 

Several important issues arose in attempting to put together both the steady-state and the dynamic simulations. The AMINES physical property package was used in both simulations and gave reasonable results in Aspen Plus. The only simulation issue in Aspen Plus was failure of the solvent recycle loop to converge. This was solved by exporting the file... 

In the original simulation, the stripper was modeled using a normal RadFrac column with a partial condenser and a total reboUer. Serious simulation issues arose when the stripper was exported to Aspen Dynamics. When a normal RadFrac model with condenser and reboiler was used (see Fig. 14.3a), the file could not be initialized in Aspen Dynamics. 

There were no dynamic simulation issues experienced in this system. The default Implicit Euler numerical integration algorithm worked well, giving quite short simulation times (1 min of real time to simulate lOh of process time). 

In this chapter the surface chemistry of selected nonsulflde flotation systems, including soluble alkali halide salts, phyllosilicates, quartz, and some naturally hydrophobic minerals, were studied using MD simulation. Issues such as water structure and dynamics, solution chemistry, interfacial water structure, and adsorption states for surfactants and macromolecules were examined. It is clear that MD simulation has been validated as a very useful tool to study the surface chemistry of certain flotation systems. As a complement to experimental studies, MD simulation analysis provides further information and understanding at the atomic level to issues such as water structure, particle dynamics, solution viscosities, mineral surface wetting characteristics, surface charge, and adsorption states. A wide application of MD simulation in the study of mineral surface chemistry is expected to have a significant impact on further advances in flotation technology. 

Simulation issues on fluidized beds are discussed from both industrial and academic viewpoints. Some state of arts of DEM simulation is reviewed focusing on agglomerating fluidization, high temperature and pressurized reactor operations. For the future investigation, research needs are discussed. 

Figure 6.22 The input voltage (top) and output current (bottom) are displayed for a I-molecule inverter (see Figure 6.21). Note that when the input is high, the output is low, and vice versa. The current spikes are due to simulation issues and would not occur in an actual NanoCell.

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