Design and simulation of seawater thermal desalination plants

Water is the most important chemical component on Earth. Seawater
distillation processes have a considerable promise as a technique
suitable for producing large scale quantities of potable water from the
seawater.
Distillation process flowsheets consist of a number of interconnected
units. The development of the mathematical model describing the
behaviour of these units, and the subsequent solution of this model are
fundamental steps in process flowsheeting.
The first objective of this work is to develop a specialized
flowsheeting program for performing design and simulation calculations
for different types and configurations of seawater distillation
processes.
Many numerical methods have been used for solving linear and
nonlinear sets of equations representing distillation processes. Most
of these methods involve the direct manipulation of the mathematical
model equations without exploiting the special properties, such as the
sparsity and the weak nonlinearities, of these equations. The second aim
of this study is to develop a new approach taking advantages of
these properties. Hence, the model equations can be linearized, and
grouped according to the variable type. These groups can then be solved
by linear matrix technique.
The performance of the developed program is investigated by solving
many distillation process problems. The results from design and
simulation calculations for large practical desalination plants are
discussed. In addition to that the convergence characteristics of the
new approach (such as stability. number of iterations. computing time.
sensitivity to starting values, and general ease of use) are presented.
Also. the validity of the approximation assumptions proposed to develop
the new approach is examined.