A pure component (or sometimes mentioned simply as component) in a SuperPro Designer simulation represents the most elementary species that make up the composition of streams and vessel contents. Ultimately all mass and energy balances in SuperPro Designer are performed at the component level. Examples of components are ‘Water’, ‘Oxygen’, ‘Nitrogen’, ‘Biomass’, etc. Please note that a pure component does not necessarily have to represent a single-molecule species. You may decide to use a pure component to represent ‘Debris’ in your process. Or, you may decide to use a pure component to represent ‘Fats’ in your process. That is acceptable, as long as you cannot expect the simulation to break such species into its constituents and as long as you provide for such components some reasonable values at least for their most commonly used properties (density, boiling point, heat capacity, etc.). There may also be times when you may need to have two ‘pure components’ representing the same species but in different forms: for example, you may need two different pure components representing the same material in dissolved state and in crystal form. That is also acceptable (see info on Sometimes it is necessary to have the same chemical substance (e.g. NaCl) represent two different forms of that substance (e.g. in soluble form and as a crystal). After you have registered NaCl as a component for the first time (to represent the soluble form), you cannot re-register NaCl. If you did you would receive the following message:). Each pure component has a whole set of properties that describes its behavior (see Pure Component Properties). You do not need to know precisely all of a component’s property values in order to introduce it in your simulation as it is possible that the simulation models you have included in your process only need a limited set of component properties. Before you can engage a component in your process simulation you must register it (see Pure Component Registration).