Introduction to Aspen Plus™ 2006.5

Engineers are constantly being called upon to predict the behavior of systems. Chemical engineers in particular must be able to predict the actions of chemical species, a very difficult task. As chemical engineering students, when confronted with a large chemical system, you might ask, "Where do I even begin? Mass balances? Energy balances? Thermodynamic properties? Reaction Kinetics?" Over the past few years as a student you've learned about each of these crucial topics separately, however, "real world" situations will require an engineer to incorporate all of these areas.

This is where the idea of a process model is helpful. A process model can be defined as an engineering system's "blue print." The process model is a complete layout of the engineering system including the following:

  1. Flowsheet
    The process model flowsheet maps out the entire system. The flowsheet shows one or more inlet streams entering into the system's first unit operation (i.e., heat exchanger, compressor, reactor, distillation column, etc.) and continues through the process, illustrating all intermediate unit operations and the interconnecting streams. The flowsheet also indicates all product streams. Each stream and unit operation is labeled and identified.

  2. Chemical Components
    The process model specifies all chemical components of the system from the necessary reactants and products, to steam and cooling water.

  3. Operating Conditions
    All unit operations in the process model are kept under particular operating conditions (i.e., temperature, pressure, size). These are usually at the discretion of the engineer, for it is the operating conditions of the process that effect the outcome of the system.

Sound confusing? Well can you imagine keeping track of all of this by hand, then solving all the mass and energy balances, determining thermodynamic behavior, and using reaction kinetics just to determine what size reactor to use, or how much product you'll achieve?

ASPEN PLUSTM allows you to create your own process model, starting with the flowsheet, then specifying the chemical components and operating conditions. ASPEN PLUSTM will take all of your specifications and, with a click of the mouse button, simulate the model. The process simulation is the action that executes all necessary calculations needed to solve the outcome of the system, hence predicting its behavior. When the calculations are complete, ASPEN PLUSTM lists the results, stream by stream and unit by unit, so you can observe what happened to the chemical species of your process model.

So continue on and check out how to use ASPEN PLUSTM as a tool in solving some reaction engineering problems.