THE SIMPLE BLOCKS - Teach Yourself the Basics of Aspen Plus - page 37

1 3

SPLIT1 4

2

5

Figure 3.3 Fsplit block.

be calculated as

p i
f i

α i = (3.3)

where f i is the combined feeds flow of component i . Componential material balances
are as follows. Let F and h represent the total flow rate and the molar enthalpy of
the combined feed streams, and let P j and α i represent the flow rate and split fraction
of the product streams. Since there are n product streams n − 1 split-fraction material
balance equations, each described by the following equation, may be written for the
product streams:

P i = α i F (3.4)

with the flow rate of the last product stream calculated by the overall material
balance

n − 1

P n = F − P k (3.5)

k = 1

The combined feed molar enthalpy, h , is assigned to each product stream. The
pressure of all the product streams is identical and is either specified on the flash
tab or if not specified, the lowest input stream pressure is used and thus all product
streams are at the same state. If the energy balance option is used for the simulation,
the temperature of a product stream is calculated by an adiabatic flash.
The Ssplit block available from the model library, except for the input format, has
the same functionality as Fsplit.

3.2 SIMPLE SEPARATOR BLOCKS

The simple separator blocks Sep and Sep2 are available from the Aspen Plus model
library shown on the bottom of the Aspen Plus displays under the Separators tab, as
shown in Figure 3.4.