Environmental Engineering Reference
In-Depth Information
Figure 26 above is showing such complete heat exchanger network that achieves the
desired heat recovery level exhibited in minimum heating utility equal to 2870 kW and
minimum cooling utility equal to 50 kW. It also consists of the estimated minimum number
of units that equal to 5 units, two process to process heat exchangers and three utiltity service
units (two heaters and one cooler).
Having introduced the fundamentals of energy integration using pinch techniques, the
second part will discuss two industrial applications. In these two application pinch technology
has been used for targeting and utility selection. However, because of capital cost and end
user preference its strict application has been sacrificed for the sake of easy to operate
networks and less capital investment.
PART
II.
H
EAT
I
NTEGRATION
A
PPLICATIONS IN
O
IL
I
NDUSTRY
Environmentally, there are essentially four phenomena associated with atmospheric
emissions. They are urban smog, acid rain, ozone layer destruction and the greenhouse effect
or global warming.
The greenhouse gas effect or global warming phenomenon problem arises mainly from
the burning of fossil fuels, and its main constituents are carbon dioxide and methane, of
which methane has more than ten times the effect of carbon dioxide. The result is that global
temperatures increase, leading to melting of the polar ice caps and thus rising sea levels,
increased weather disruptions and changes to ocean currents. Atmospheric emissions are
mainly formed as by-products of combustion processes. Such combustion processes, to date,
remain to be the main source used for energy generation in our societies.
In process industries, the essential sources of energy waste are associated with hot
utilities. If the process industries require a furnace or a boiler to provide hot utility, then any
excessive use of the hot utility will automatically produce excessive utility waste and
consequently excessive generation of atmospheric emissions.
Therefore, energy conservation is one important way of not only saving money and
natural resources, but also protecting the environment via minimizing energy-based GHG
emissions. Until late last century the preferred method of dealing with the atmospheric
emissions were known to be taking the end-of-pipe approach. This approach is myopic view
and usually an expensive one.
This view does not tackle the problem at the source where solving could and indeed has
proved in many cases to be easier and more cost effective. Nowadays, energy efficiency
optimization techniques have become a major tool in NO
x
, SO
x
, CO and CO
2
emissions
minimization from combustion-based processes.
Systematic methods and tools have been developed and are currently utilized to conserve
energy; protect energy-based natural resources and last but not least to minimize energy-
based emissions and reduce the impact on the environment.
A major concept in the energy efficiency optimization techniques is the concept of “Heat
Integration” applied in Pinch Technology and others to enhance waste energy recovery in
industrial processes. One way of using this concept is to look first in our plants to satisfy
some of their thermal energy needs through letting the hot streams (sources) that are to be
