Feed Block with Flash

Feed Blocks are used to represent sources of material in Flowsheets. In some cases, users may have a situation where a feed stream may be in a multi-phase state, but may not know the full details of the equilibrium state. The IDAES Feed Block with Flash (FeedFlash) allows users to define a feed block where the outlet is in phase equilibrium based on calculations from the chosen property package and a sufficient set of state variables prior to being passed to the first unit operation. The phase equilibrium is performed assuming an isobaric and isothermal flash operation.

A Feed Block with Flash is only required in cases where the feed may be in phase equilibrium AND the chosen property package uses a state definition that includes phase separations. Some property packages support phase equilibrium, but use a state definition that involves only total flows - in these cases a flash calculation is performed at the inlet of every unit and thus it is not necessary to perform a flash calculation at the feed block.

Degrees of Freedom

The degrees of freedom of FeedFlash blocks depends on the property package being used and the number of state variables necessary to fully define the system. Users should refer to documentation on the property package they are using.

Model Structure

FeedFlash Blocks contain a single ControlVolume0D (named control_volume) with one Outlet Port (named outlet). FeedFlash Blocks also contain References to the state variables defined within the inlet StateBlock of the ControlVolume (representing the unflashed state of the feed).

FeedFlash Blocks do not write a set of energy balances within the Control Volume - instead a constraint is written which enforces an isothermal flash.

Additional Constraints

The FeedFlash Block writes one additional constraint to enforce isothermal behavior.

\[T_{in, t} = T_{out, t}\]

where \(T_{in, t}\) and \(T_{out, t}\) are the temperatures of the material before and after the flash operation.


FeedFlash blocks add no additional Variables.

FeedFlash Class

class idaes.unit_models.feed_flash.FeedFlash(*args, **kwargs)
  • rule (function) – A rule function or None. Default rule calls build().
  • concrete (bool) – If True, make this a toplevel model. Default - False.
  • ctype (str) – Pyomo ctype of the block. Default - “Block”
  • default (dict) –

    Default ProcessBlockData config

    Feed units do not support dynamic behavior.
    Feed units do not have defined volume, thus this must be False.
    Indicates what type of material balance should be constructed, default - MaterialBalanceType.componentPhase. Valid values: { MaterialBalanceType.none - exclude material balances, MaterialBalanceType.componentPhase - use phase component balances, MaterialBalanceType.componentTotal - use total component balances, MaterialBalanceType.elementTotal - use total element balances, MaterialBalanceType.total - use total material balance.}
    Indicates what type of flash operation should be used. default - FlashType.isothermal. Valid values: { FlashType.isothermal - specify temperature, FlashType.isenthalpic - specify enthalpy.}
    Property parameter object used to define property calculations, default - useDefault. Valid values: { useDefault - use default package from parent model or flowsheet, PhysicalParameterObject - a PhysicalParameterBlock object.}
    A ConfigBlock with arguments to be passed to a property block(s) and used when constructing these, default - None. Valid values: { see property package for documentation.}
  • initialize (dict) – ProcessBlockData config for individual elements. Keys are BlockData indexes and values are dictionaries described under the “default” argument above.
  • idx_map (function) – Function to take the index of a BlockData element and return the index in the initialize dict from which to read arguments. This can be provided to overide the default behavior of matching the BlockData index exactly to the index in initialize.

(FeedFlash) New instance

FeedFlashData Class

class idaes.unit_models.feed_flash.FeedFlashData(component)[source]

Standard Feed block with phase equilibrium


Begin building model.