Page 340 - Sustainability in the Process Industry Integration and Optimization

Co n c l u s i o n s a n d Fu r t h e r I n f o r m a t i o n 317

Increasing the efficiency of process systems via PI increases the
importance of this issue because PI also increases the interdependence
of the various process modules and subsystems. Cheung and Hui
(2004) proposed a scheme for Total Site maintenance scheduling for
better energy utilization. To minimize the impacts on production
and utility systems during routine maintenance, the scheduling
must be done carefully and with consideration of sitewide utilities
and material balances. The reliability analysis targets maintenance
requirements, cost, availability, and maintainability. The method-
ology described by Yin et al. (2009) considers flexible process design
simultaneously with reliability and risk factors, and the best
solutions are obtained by optimizing the PI. Sikos and Klemeš
(2010a, 2010b) applied a combination of HEN optimization and
reliability software packages to develop a methodology with several
advantages over the commonly used approach.

14.2.3 Hybrid Energy Conversion Systems
Energy conversion systems for heat and power generation
traditionally involve only gas and steam turbines. However, the
interest of research and industrial engineers has recently been
attracted by a broader range of technologies: the hybrid energy
conversion systems involving fuel cells (FCs). Especially interesting
are high-temperature fuel cells (HTFCs), which feature electrical
efficiency of 40–60 percent (Yamamoto, 2000) compared with
30–35 percent for most gas turbines (Gas Turbine World, 2001). There
has been an extensive research aimed at improving the efficiency of
FC systems. Karvountzi, Price, and Duby (2004) compared the
integration of molten carbonate fuel cells (MCFCs) and solid oxide
fuel cells (SOFCs) into hybrid systems. Kurz (2005) focused on the
choice of appropriate gas turbines for the given FCs, and Massardo
and Bosio (2002) studied the MCFC combinations with gas and
steam turbines. One promising option is to integrate the FCs with
“bottoming cycles” for dedicated power generation or Combined
Heat and Power applications. Varbanov et al. (2006) and Varbanov
and Klemeš (2008) studied the benefits of integrating HTFC systems
with steam cycles for purposes of industrial cogeneration. The
results indicate that HTFCs have great potential in terms of economic
viability and a low carbon footprint.

14.2.4 Integration of Renewables and Waste
Most energy systems of industrial, residential, service and business,
agriculture, and production sites continue to use fossil fuels as their
primary energy source. Sites are usually equipped with steam and/
or gas turbines and with steam boilers and water heaters (running on
electricity or gas) as energy conversion units. The challenge of
increasing the share of renewables in the primary energy mix could
be met by integrating solar, wind, biomass, and some types of waste