Types of Streams
Depending on the nature of the material that is represented by a stream, SuperPro Designer distinguishes between two types of streams:
a) Bulk Streams
b) Discrete Streams
Bulk streams carry material measured by flowrate units:
(mass-or-volume units) / (time units), or (mass-or-volume units) / batch.
Part of the material can be in liquid, gaseous or solid phase but SuperPro Designer distinguishes only two phases: liquid/solid and vapor. The flow of discrete streams on the other hand, is measured in:
(Entities) / (time units) or (Entities) / batch.
Each discrete stream carries one and only one type of entity (e.g. ‘12oz Plastic Bottle’). The definition of the entity carried by an input stream is done as part of the initialization of the stream (see Discrete Input Streams). For intermediate or output discrete streams, the definition and description of the entity carried by the stream is inferred (or retrieved) from the operation in the procedure that originally produces the entity. When streams are connected to a unit procedure (as their source or destination), they are attached to one of its input or output ports (see Unit Procedure Ports). Bulk streams can only be attached to bulk-stream ports and discrete streams can only be attached to discrete-stream ports.
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You do not have to explicitly set the stream type as bulk or discrete. SuperPro Designer automatically decides their type based on the context (type of port that it is connected). If you start a stream by clicking on a procedure’s output port, SuperPro Designer automatically creates the correct stream type (bulk or discrete) depending on the type of the port that you started. When creating an input stream, SuperPro Designer will decide the nature of the stream only after you have clicked on a destination port. The application will not allow you to hook-up a discrete stream to a bulk port and vice versa.
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Every stream must have either a source or a destination procedure or both. There can’t be a stream that has no source and no destination procedure. Based on the presence or absence of a source and/or a destination procedure, a stream is characterized as:
a) Input Stream: a stream that has no source procedure.
b) Intermediate Stream: a stream that has both a source and a destination procedure.
c) Output Stream: a stream that has no destination procedure.
For input streams, most of their properties (such as pressure, temperature, flow and composition) must be specified by the user. All properties of intermediate and output streams are calculated as part of the simulation results (after the M&E balances are executed) and they cannot be edited by the user. The only attributes of intermediate streams that can be edited are those related to the determination of the physical state of the stream and its density (a.k.a, the Physical State Toolbox). This is done through the Bulk Intermediate/Output Stream Dialog: Physical State Tab
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When viewing the composition of output or intermediate streams on their i/o dialog (see Viewing and Editing the Simulation Data of Bulk Streams), components with zero flowrates are not reported. Input streams on the other hand will display all ingredients introduced in the composition table (regardless of their assigned flow value).
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From the standpoint of process economics, streams contribute differently depending on how they are classified. SuperPro Designer considers the following nine types of classifications for streams:
a) Raw Material
b) Revenue or Credit
c) Cleaning Agent
d) Waste (Solid Waste, Organic Waste, Aqueous Waste, or Emission)
e) None (Un-classified).
Only input streams can be classified as ‘Raw Material’ and only output streams can be classified as ‘Waste’ (of any type). Unlike the previous stream types (bulk vs discrete and input vs output/intermediate) that are automatically assumed by the application based on the inherent nature of the stream, the economic stream classification must be done explicitly by the user. For more details, see Classification of Input and Output Streams.