Aspen: Analysis or simulation
- An overview of Aspen Plus
- Modeling concepts in Aspen Plus
- Features of Aspen Plus
- Options of Aspen Plus
- Key components in Aspen Plus
- Literature review
- Sensitivity analysis
- Introduction to reactive distillation (RD)
- Background study
- RD modeling
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. [...]
[...] Aspen Plus is a great tool for the development of chemical processes or carrying out analysis on existing processes industry as a design tool because of its ability to simulate a variety of steady-state processes ranging from single unit operation to complex processes involving many units. Solving equations of state allows us to find the specific volume of a gaseous mixture of chemicals at a specified temperature and pressure. Without using equations of state, it would be virtually impossible to design a chemical plant. [...]