Environmental Engineering Reference
In-Depth Information
chapter, only the first few levels of design are discussed, beginning with the positioning
of a process in a supply chain and ending with functional block diagrams of processes.
Special attention is given to the integration of process units into the overall process
design, setting a stage for the coverage of conversion units in the next part of this topic.
In view of the introductory nature of this chapter, the following subjects will be
skipped:
a. Modeling and simulation of processes by means of process flow sheeting,
e.g., ASPEN
®
b. Process integration of energy, solvents, and utilities by matching suitable
sources and sinks within the process
c. Equipment design
d. Safety and control engineering
Making some shortcuts in presenting this process design topic is unavoidable. General
and deeper reading on chemical process design is offered by, among others, the fol-
lowing textbooks: Douglas (1988), Smith (2005), and Biegler et al. (1997). Textbooks
focused on analysis, design, and optimization of integrated biorefineries have recently
appeared (see, e.g., Stuart and El-Halwagi, 2012).
7.2 CHARACTERIZATION OF BIOMASS PROCESSING
The focus of this topic is the conversion of the chemical energy stored in biomass into
other forms of energy. The selection and proper modeling of such a route is the field
of process design. There are a number of reasons that make the design of biomass
conversion processes challenging: the wide variety of feeds, the many different
processing options and the broad product spectrum.
7.2.1 Wide Variety of Feeds
As discussed in Chapter 2, there are many different types of biomass, with very different
compositions, that can be used as feed for biomass conversion processes. In addition, a
single type of biomass might also vary strongly in composition over time, due to sea-
sonal influences or different places of origin. In addition to the biomass feeds, most
processes will also require nonbiomass feed, e.g., air for combustion, gasification, or
fermentation. In some cases, a mixture of biomass with other energy-containing feeds
(fossil fuels) is used. A proper characterization of the chemical structure and composi-
tion of a biomass feed and its variability is essential for process design (see Chapter 2).
7.2.2 Wide Variety of Processing Options
There are many different ways to convert biomass, thermochemical conversion and
biochemical conversion being the two most important categories, as discussed in
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