Page 495 - Industrial Wastewater Treatment, Recycling and Reuse

Simulation, Control, and Optimization of Water Systems in Industrial Plants 465

• Reduce tedious and time-consuming experimentation.
• Present the process in a mathematical language suitable for computer
solution.
• Apply this representation in several case studies and across software
platforms.
A modern chemical plant consists of interconnected units such as heat
exchangers, reactors, distillation columns, and mixers with a high degree of
integrationtoachieveenergyefficiency.Designandoperationofsuchcomplex
plants is a challenging problem that could be easily carried out by simulation
software.Ingeneral,wheneverthereisaneedtomodelandanalyzerandomness
in a system, simulation is the tool of choice. More specifically, situations in
which modeling, simulation, and analysis are used include the following:
• When it is impossible or extremely expensive to observe certain pro-
cesses in the practical world.
• When problems arise in which a mathematical model can be formulated
but where analytic solutions are either impossible or too complicated.
In the past, traditional methods have relied heavily on expensive experimen-
tation and the building of scaled models, but now a more flexible and cost-
effective approach is available through greater use of mathematical modeling
and computer simulation. Computer-aided modeling, simulation, and opti-
mization save time and money by reducing the effort in the configuration of
experimental work. In addition, computer simulation and optimization save
money in design and operation. The long-term performance and reliability
varies from plant to plant and day to day for various reasons such as operating
conditions, scaling, and fouling of heat transfer surfaces in boilers and water
treatment units. Therefore, better operation of the existing plant depends on
the better understanding of the different parameters of the plant. Simulation
helps to visualize the ultimate picture and trends of various conditions
of existing plant as well as those of a new situation arising out of any
process/parameter changes in the plant.
A mathematical model is a collection of (a set of) equations that describe
some aspects of the chemical system under investigation. For many complex
chemical processes, the model result is a set of nonlinear equations requiring
numerical solution. The most common way to deal with this is to program
the equations using modeling software such as Aspen Custom Modeler
(ACM) or other engineering software.
An industrial process has a lifecycle from conception through R & D,
engineering, commissioning, operations, and decommissioning. A good
mathematical model (also called a process model) can assist the activities