PROCESSES: BASICS OF PROCESS DESIGN - Biomass as a Sustainable Energy Source for the Future - page 225

process block diagram showing the required processing units. To ensure a successful
integration of process units into a flow sheet, some specifications are formulated
regarding the required design information and models for these units. At each design
level, designers can follow the same sequence of generic steps, involving setting of
design specs, synthesis of structure, analysis of physical behavior, and evaluation
of performance. FT synthesis of liquid fuels from syngas is presented as a process
example.

KEY CONCEPTS

Process design: decision making with a host of choices and many constraints
Decision making: hierarchical by distribution over multiple levels (7) of increasing
detail
Generic engineering design steps, applicable at each level
Resulting matrix for conceptual process design
Iterative passes over engineering design steps and levels: often necessary to improve
process designs
Input output and functional block diagrams

Molar balances for a process block diagram with an economic potential function,
solved for design analysis and evaluation

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SHORT-ANSWER QUESTIONS

7.1 Who are the key stakeholders for a plant design for the conversion of lignocel-
lulosic biomass into chemicals, heat, and power? Make a list of these stake-
holders and give several performance criteria examples that each stakeholder
will consider important for the design. It is recommended to use this format
when making the list: (A) Stake holder category A, (A1) Stakeholder A1, Per-
formance Criterion A1a, Performance Criterion A1b, and so on.

7.2 Give examples of the internal multiscale structures in a process (from enterprise
down to the molecule level).

7.3 In the synthesis step of a design, one must identify suitable building blocks and
connect them to a network. Give some examples of different types of building
blocks and connections for a thermochemical process. What is the kind of
knowledge that you would look for to get an understanding of the relevant
design features of a block?

7.4 Describe the difference between the analysis of a process, using models, and
evaluation of the performance of a process.

7.5 In the hierarchical decomposition approach to process design, the design deci-
sion variables are portioned in a hierarchy of smaller clusters (levels). Decisions
that are taken at the top level consider those decision variables that have a high