Environmental Engineering Reference
In-Depth Information
(tinyurl.com/yocw7q). Since designs with performance points on a Pareto frontier
curve cannot be further optimized, the selection of a specific design from this critical
set must be guided by company policy regarding economy and ecology (
“
people,
planet, profit
).
Having analyzed the more common outside and inside aspects of a process, the
scene is set for the introduction of a process design procedure. Such a procedure aims
primarily at creating a well-structured flow in making rational design decisions, based
on domain knowledge. Such domain knowledge of biomass processing (thermody-
namics, reaction kinetics, physical transport phenomena, and equipment) can be
obtained from Chapters 8
”
-
15.
7.5 A DESIGN PROCEDURE FOR BIOMASS
CONVERSION PROCESSES
7.5.1 What Is the Design Problem?
The design of processes for biomass conversion is very similar to the design of other
chemical processes. The key distinction is the solid-phase biomass feed, having
a complex and varying composition. In any process design, one must consider the
following issues and make decisions:
Which physical, chemical, and mechanical processing operations are needed to
go from feed(s) to product(s)?
How to order and connect these processing operations? Are recycles of uncon-
verted feed and solvents possible?
Which solvents and catalysts are to be used as active agents in the processing?
Should heat sources and heat sinks in the process be connected and in what way?
In which type of equipment can each operation best be conducted?
Which mode of operation of the equipment (batch, continuous) is most suitable?
What are suitable operating conditions (temperature, pressure, thermodynamic
phases) in the equipment?
Howmuch residence time is needed in the equipment per thermodynamic phase?
How to design the equipment internally (compartmentalization, internals)?
What should be the target uptime of the process?
How reliable should be the equipment in its operation (as to meet this target
uptime)?
Are risks of failure (economic, ecological, technological) sufficiently small?
Is the expected performance of the design satisfactory?
The design decision variables in many of the above design questions are of a
discrete
nature; the variable can take only a few distinct values. For example, equipment, is it
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