A process consists of chemical components being mixed, separated, heated, cooled, and converted by unit operations. These components are transferred from unit to unit through process. Process flow sheet can simply be defined as a blue print of a plant or the language of chemical processes. Like a work of art, they describe an existing process or a hypothetical process in sufficient detail to convey the essential features. It identifies all feed streams, unit operations, streams that inter-connect the unit operations and finally the product streams. Operating conditions and other technical details are included depending on the detail level of the flow sheet. The level can vary from a rough sketch to a very detailed design specification of a complex plant.
For steady-state operation, any process flow sheet leads to a finite set of algebraic equations. For a case where we have only one reactor with appropriate feed and product streams the number of equations may be manageable by manual hand calculations or simple computer applications. However, as the complexity of a flow sheet increases and when distillation columns, heat exchangers, absorbers with many purge and recycle streams come into the picture the number of equations easily approach many ten thousands. In these cases, solving the set of algebraic equations becomes a challenge in itself. However, there are computer applications called process flow sheet simulators specialized in solving these kinds of large equation sets. Some well known process flow sheet simulators are Aspen Plus, ChemCad and PRO/II. These products have highly refined user interfaces and on-line component databases. They are used in real world applications from interpreting laboratory scale data to monitoring a full scale plant.
[...] For the simulation of this the reflux ratio and the distillate rate were specified in addition to the feed rates and the column setup. Parameter Values Used in Aspen Plus Simulation Procedure: Building the Flow sheet: First step is to draw the flow diagram in the Process flow diagram (PFD) window. Chosen equipment from the Model Library and placed it on the flow sheet by dragging it to the blank (white) area of the screen. Here RadFrac has been chosen from the columns tab, which is a rigorous, multi component, multiphase distillation column model. [...]
[...] Fig 4.11 Effect pressure on Methanol conversion Methyl acetate purity in distillate Reactive zone tempera Catalyst Distribution among Reactive Stages Starting from the 12th stage downwards, the fixed total catalyst load corresponding to the case study was uniformly distributed among several contiguous reactive stages whose number was varied from 12 to 19.The simulation studies show that when more catalyst is used, more product will be generated. However, if the product generated by the reaction is too great to be separated from the system, chemical equilibrium will force the reaction in the wrong direction. [...]
[...] The input specifications for the simulation are based on the design specifications of the rectification column. A base case model is developed by the rigorous simulation model in Aspen Plus (RadFrac), with suitable thermodynamic model chosen. Shortcut simulation and manual calculation are carried out to estimate some parameters for rigorous simulation. Next, sensitivity analysis is carried out for the base case model, in which will help us to determine the parameters to be optimized and its range for optimization. Finally, parametric optimization is performed to obtain the optimum operating conditions of the rectification column Introduction Rectification is one of the distillation techniques which are widely used in industry. [...]
[...] Fig Material Streams window The Data Browser The Data Browser is a sheet and form viewer with a hierarchical tree view of the available simulation input, results, and objects that have been defined. Click the Data Browser button on the toolbar to open the Data Browser. Fig Data Browser window All of the data input for Aspen Plus is entered in the Data Browser window. Aspen Plus has two features in the Data Browser window that can both help and hurt the user. [...]
[...] In this research, sensitivity analysis is done to identify the critical variables or parameters, and the range of parameter for optimization. The results of this analysis are illustrated in Fig 3.14 to Fig 3.14 Purity and duty versus feed flow Fig 3.15 Purity and duty versus feed stage Fig 3.16 Purity and duty versus feed pressure Fig 3.17 Purity and duty versus mole reflux ratio Fig 3.18 Purity and duty versus mole reflux ratio Fig 3.19 Purity and duty versus mole Feed Temperature Discussion: Figure 3.15 and 3.16 shows that heat duty of reboiler and condenser are less sensitive to the feed location and feed pressure (within certain range). [...]
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