Information Technology Reference
In-Depth Information
CHAPTER TWELVE
PROCESS FLOWSHEET DEVELOPMENT
Prior to this chapter, most of the Aspen Plus blocks have been introduced and the
reader has gained experience in their use. This chapter deals with the integration of
blocks into a process flow diagram (PFD), which is the source document for the process
engineering function of producing process and instrument diagrams (P&IDs). A typical
PFD contains process details of each processing unit and all reaction units, connected
by the main process lines. Each unit operation and reaction unit will contain basic
design data, such as operating temperature and pressure, and limited equipment design
data, such as the number of theoretical stages required. Additionally, the presence of
trace components will be identified, although it is not unusual that some surprises
arise. Very few detail design data are included on a PFD, nor are instrumentation
and process control requirements, operating instructions, equipment redundancy, safety
considerations, shutdown and startup requirements, and the myriad other details that
are the responsibility of the P&ID developers.
The PFD development process begins with a process description typically based on
small-scale chemical experiments and larger-scale minipilot and pilot-plant scale work.
Additionally, a collection of physical and thermodynamic property data is developed
by experimentation, collected from the literature, and estimated if necessary. These are
used to produce a block diagram of the process, which is usually nothing more than a
material balance that includes many performance estimates based on laboratory work
and, in some cases, guesstimates.
12.1 HEURISTICS
When developing a process flow diagram, the following experience-based ideas are
worthwhile:
