Page 226 - Sustainability in the Process Industry Integration and Optimization

S o f t wa r e T o o l s 203

key equipment, such as heat exchangers and distillation columns,
within the simulation environment.

9.5.2 HYSYS and UniSim Design
The HYSYS software was initially created by Hyprotech for
simulating both steady-state and dynamic processes. It includes tools
that can be applied to: (1) estimating physical properties, including
liquid–vapor phase equilibrium; (2) establishing heat and mass
balances; (3) designing and optimizing oil and gas processes; and
(4) evaluating and selecting process equipment. HYSYS technology
was acquired and modified by Aspen (see Section 9.5.1) and later by
Honeywell, where it is known as UniSim Design (Honeywell, 2010).
Aspen HYSYS and UniSim Design are similar in terms of application
and the working interface. Both include: (1) a library of physical
properties of many chemical substances; (2) a set of subroutines for
estimating the behavior of several types of plant equipment (heat
exchangers, reactors, etc.); and (3) a graphical user interface for
inputting case specifications and displaying results.
Once the designer describes the process in terms of equipment
units interconnected by process streams, the program solves all the
equations for mass, energy, and equilibrium while taking into
consideration the units’ specified design parameters. The program
is built upon proven technologies that for two decades have supplied
process simulation tools to the oil and gas industry. Another
advantage of Aspen HYSYS and UniSim Design is their interactive
and flexible process modeling, which allows engineers to design,
monitor, and troubleshoot as well as to make operational
improvements and perform asset management. Employing these
features leads to decision making that enhances the productivity,
reliability, and profitability of a processing plant’s life cycle
(Ebenezer, 2005). The HYSYS “fluid package” module requires
information on the characteristics of unit components and the
physical properties of relevant streams. Also, accurate simulation of
processes requires that appropriate thermodynamic models be
selected as a framework for the simulation. Note that a process that
is otherwise fully optimized in terms of equipment selection,
configuration, and operation is of no use whatsoever if the process
simulation was based on an incomplete or inaccurate fluid package
or on an inappropriate thermodynamic model.
HYSYS requires minimal input data from the user; the most
important input parameters are the stream’s temperature, pressure,
and flow rate (Ebenezer, 2005). The software includes an assortment
of utilities that can be attached to process stream and unit operations.
These tools interact with the process to provide valuable additional
information. For example, the flowsheet used within the HYSYS
simulation environment can be manipulated by the designer to
estimate desired output.