Discrete streams represent the flow of discrete entities (e.g. a “2L Plastic Bottle”). Discrete streams are only allowed to connect to discrete (input or output) ports of procedure icons. Their flowrate is measured in Entities/h (for processes in continuous mode) or Entities/batch (for processes in batch mode). Each discrete stream can only carry one type of entity.
An entity is any matter that can be carried by a stream in discrete quantities (in contrast to bulk material that can be carried by a stream in any quantity). Examples of entities can be: a “1L Empty Bottle”, a “12oz Filled Can”, a “Mid-Size Box”, an “Empty Six-Pack”, etc. Users may engage such discrete entities to describe the contents of (discrete) streams. For example, in order to describe the contents of a line with soon-to-be-filled empty 12oz bottles, we need to introduce the entity of “Empty 12oz Bottle”. In order to define an entity you need to provide the following attributes:
1. Name: A string of up to 31 characters; it must be unique amongst all entities defined in a process.
2. Bulk Amount per Entity: Allows the program to convert the bulk equivalent mass into discrete entities; it can be either in mass or volume units.
3. Purchase Price: used when this entity is being sold (on a ‘Revenue’ output stream)
4. Selling Price: used when this entity is being purchased (on a ‘Raw Material’ input stream)
Unlike pure components or stock mixtures, entities are not formally registered in a process through a central interface. Instead, they are defined at the spot where they are needed. There are only two locations where entities can be defined:
a) As part of a discrete input stream that describes the feed of discrete entities into the process (such as the line of empty 12oz bottles mentioned above). In that case, the four essential properties of the entity (name, bulk amount per entity, selling and purchase price) are directly provided on the Discrete Input Stream Dialog: Entity Tab.
b) As part of an operation that produces an entity (e.g. a filling operation, or a packaging operation, etc.). To continue with the example of empty 12oz bottles mentioned previously, once those bottles are fed into a filling operation, on the other side, we need to have an output of “Filled 12oz Bottles”. In that case, users get the chance to define this new entity as part of the operation that will combine one (previously defined) entity and perhaps some bulk material. Other times, an operation may use (consume) all bulk streams but generate (output) a discrete entit: e.g. a molding operation or a tableting operation. Other times the operation may consume one (or more) discrete lines and produce (output) a new entity line: e.g. a labelling operation, an assembly operation, etc. In all such cases, the four essential properties of the new entity that is being produced by the operation are defined as part of the ‘Oper. Cond’s’ tab of the operation that produces it.
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The properties of a discrete entity will be displayed on every discrete stream that carries it but can only be changed from the interface that introduces the entity: either the i/o simulation dialog of the discrete input stream where the entity first enters the process, or the i/o simulation dialog of the operation that is responsible for first manufacturing the entity. |
Discrete input streams represent material that is being fed into a process in the form of such countable (discrete) entities. Even though users must specify the flow of such streams in terms of entities/h or entities/batch, they must still have to describe to the application the composition of the bulk material that makes up the entity. For example, if the discrete input stream is to represent the flow of empty (but soon to be filled) aluminum 12oz cans, you can describe the composition of the bulk material as 100% Aluminum; if the input stream represents the flow of empty (to be filled) vials, you can specify the composition of the bulk material as 100% glass. The information about the composition of the bulk material may be used if the entity is ever processed through an operation that converts it back to the bulk material that it is made. For example, consider a grinding operation or shredding operation, or even the generic ‘discrete-to-bulk’ operation. Please note that the composition of the bulk material that each entity is constructed is provided in the second tab (the Input Stream Dialog: Composition, etc. Tab). The first tab of the stream’s i/o dialog is dedicated to defining the entity that is carried by the stream, and thus it provides for fields that will capture the four essential properties of the entity carried by the stream (see The ‘Entity’ tab (entity definition) on a discrete input stream.).
The ‘Entity’ tab (entity definition) on a discrete input stream.
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If the ‘auto-adjust’ flag is checked on a discrete input stream, the entity flow of the stream will be determined by the application. For example, in a bottle-filling operation, once the bulk material comes into the bottling step (as the bulk input) and the user specifies the amount of bulk material to be added per bottle (as part of the operation’s i/o dialog), then the other input of the operation (carrying empty bottles) will have it entity flow automatically adjusted so that all the bulk material is properly accommodated. |
The density-related information of discrete input streams, pertains to the density of the bulk material that makes up each entity. It will be used by the application only if the ‘bulk amount per entity’ specification for the entity is in volume units. If that is the case, then in order for the application to determine the entity flow for the stream, it will need to convert the bulk mass into volume and then use the ‘bulk amount per entity’ factor to determine the number of entities carried by the stream. The density of the bulk material can either be provided by the user or be calculated by the application using the volumetric contribution model. This is specified in the Discrete Stream Dialog: Density Tab.
You can display the i/o simulation dialog of discrete streams in just the same way as for bulk streams (see Viewing and Editing the Simulation Data of Bulk Streams). Some of the variables that characterize bulk streams are not present on discrete streams (e.g. temperature, pressure, enthalpy). Furthermore, discrete streams always present information about the entity that is being carried by the stream (name, bulk amount per entity, etc.). Users are allowed to edit the entity definition parameters, the entity flow as well as the bulk material composition on discrete input streams. Discrete intermediate and output streams have all such information filled-in by the mass and energy balance calculations. Consequently, all such date are only presented on the i/o simulation dialog for display only.
