Comparison of shortcut methods for designing of divided wall columns for separating tertiary zeotropic mixtures

Recently, divided wall column has been considered as one of the types of thermally coupled towers for separating multicomponent mixtures. In the structure of this tower, there is a wall that divides the tower into two parts, the Prefractionator and the Main Column. The divided wall column is thermodynamically equivalent of the Petlyuk tower. Therefore, in order to obtain the design and simulation parameters of the Petlyuk tower utilizing the available software, this tower must be divided into simpler towers. The shortcut method is employed to acquire the initial parameters. In the present research, initially, the design of divided wall column has been conducted using shortcut methods to separate three-component zeotropic mixtures. Next, the design and simulation of the divided wall column is performed employing ASPEN PLUS software and the results of the two methods are compared from various angles.

Shortcut Method for Initialization of Dividing Wall Columns and Estimating Pareto-Optimal NQ-curves

<p>In early project stages often no simulation results are available for dividing wall columns. Hence, shortcut methods are used to estimate suitable vapor and liquid splits. In a previous paper it was shown that Vmin diagrams are a suited tool to satisfy this need. However, it has turned out that it shows weaknesses for columns with finite or non-optimal stages. This contribution closes that gap and presents an extended approach to derive suited initial guesses. For this purpose, the original Vmin diagram is combined with a heuristic approach to calculate Pareto-optimal column designs resulting in a stage-adapted Vmin diagram. A comparative study shows that the new approach is a powerful tool to generate reliable guesses for multiple dividing wall column simulations with finite stage numbers.</p>

Shortcut Method for Initialization of Dividing Wall Columns and Estimating Pareto-Optimal NQ-curves

<p>In early project stages often no simulation results are available for dividing wall columns. Hence, shortcut methods are used to estimate suitable vapor and liquid splits. In a previous paper it was shown that Vmin diagrams are a suited tool to satisfy this need. However, it has turned out that it shows weaknesses for columns with finite or non-optimal stages. This contribution closes that gap and presents an extended approach to derive suited initial guesses. For this purpose, the original Vmin diagram is combined with a heuristic approach to calculate Pareto-optimal column designs resulting in a stage-adapted Vmin diagram. A comparative study shows that the new approach is a powerful tool to generate reliable guesses for multiple dividing wall column simulations with finite stage numbers.</p>

A preliminary environmental analysis for a sustainable pyrolysis process of Acacia tortilis encroacher bush.

A shortcut method of environmental assessment was applied procedurally to an Acacia Tortillis pyrolysis project which is in early stages of process development. The method uses mass balance data from the process simulation, which is done in ChemCAD. The ChemCAD model was developed using characterization data for raw biomass and the product bio-oil and data from literature. The shortcut assessment method started off by scoring the impact of inputs and outputs as high (A=1), medium (B= 0.3) and very low (C= 0) under impact categories such as raw material availability, use of critical materials, chronic toxicity, global warming potential, odour and eutrophication potential. An aggregated metric called the general effect index (GEI) was then calculated using this data and mass indices derived from mass balance. The GEI was calculated for inputs, outputs and the overall process. It fell within the scale of 0-1, with values below 0.5 indicating a low environmental impact, while those above that threshold indicated high impact. A GEI of 0 for the inputs reflected on the renewability of biomass and neutral impact of nitrogen and air. A GEI of 0.370 for the outputs showed they do have a significant effect on the environment and organisms, though overall, the process is relatively benign. The impact could be further reduced by utilizing the fuel gas waste stream which has a high methane content. The results obtained generally tally with other literary findings on biomass pyrolysis.

Shortcut Method for "L" and "Z" Pipe Bend Sizing

In the engineering practice it may often prove necessary to provide quick and relatively accurate estimates of piping routing and material requirements in very early stages of a project. In these cases there is typically no time to perform detailed pipe stress analysis in order to obtain accurate routing which allows for sufficient piping system flexibility and the designer is constrained to the use of rule of thumb approach and good engineering judgment. This approach, although often used, may prove challenging in many situations, one of which is establishing sufficient pipe loop dimensions. Method proposed by the authors in [1] provides a procedure for quick estimation of U loops while the present procedure aims to provide additional procedures for estimation of L and Z bends, thus completing the circle of shortcut methods for quick estimation of expansion requirements of piping systems.