Page 220 - Sustainability in the process industry

S o f t wa r e T o o l s 197

to plan infrastructure investment when operational changes are
anticipated, changes that may include the replacement of energy
equipment. STAR can also be used to investigate flue gas emissions,
which should often be reduced to meet tighter environmental
regulations. The STAR package incorporates several tools, as
described next.
Utility system optimization: A given utility system configuration
incorporates important degrees of freedom for optimization.
Multiple boilers with different efficiencies and different fuels in
addition to multiple back-pressure steam turbines, condensing
turbines, gas turbine heat recovery steam generators, and letdown
valves provide optional heat flow paths that can all be exploited for
significant cost reduction. STAR has a utility system optimization
facility that allows existing utility systems to be optimized. It can
also be used to plan infrastructure de-bottlenecking and investment
strategies.
Top-level analysis: When studying an existing site, it is important
to understand how its infrastructure influences the degrees of
freedom to make changes as well as the economic consequences of
those changes. These considerations are addressed by STAR’s top-
level analysis, whose results ensure that the designer does not waste
time and costs pursuing changes that are not viable (structurally or
economically) in the overall site context.
Process energy targets: Even though the primary function of STAR
is the analysis of utility systems, it includes tools for setting energy
targets and selecting utilities for individual processes. Using these
tools allows the picture of the Total Site to be built up from the
individual processes within STAR.
Total Sites: STAR can produce profiles that represent the heating
and cooling requirements of the Total Site. This allows targets to be
set for fuel consumption in the boilers, cogeneration potential, and
energy costs. The Site Profiles can be based either on the full heat
recovery data or, more simply, on data for the utility exchangers
only.
Boiler systems and steam turbine systems: Using STAR allows the
designer to establish optimal targets for the amount of steam
generated by boilers and gas turbines (with auxiliary firing options).
A gas turbine model enables the study of different gas turbine
arrangements. Steam turbines are a part of most utility systems,
serving to generate power or as allocated drivers for process
machines. STAR software incorporates the design of steam turbine
networks and the analysis of their operability.
Emissions: By relating process energy requirements to the supply
of utilities, it is possible to target the amount of fuel required for the
utility system. Such targets can be combined with information on the