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Problem statement

This report will compare to systems, one with one separator and one with 2 of the

separation of a mixture containing n-Hexane, n-Heptane and n-Octane. Then inletmolar fractions of the 3 components are:

3.0

4.0

3.0

188

167

146

=

=

=

HC

HC

HC

x

x

x

The inlet feed has a temperature of 6o!.

Selection of equation of state

There are a few reason the "#$ e%uation of state setting was used. The "#$ setting

uses the "oar&e-#edlich-$wong method to determine the properties of the

components of the streams, it is suita'le 'ecause all chemicals present are non-

polar and this e%uation is only &alid for non-polar chemicals. This e%uation of state

has ad&antages o&er other e%uations of state. (or example the 'asic #edlich-$wonge%uation can 'e used, howe&er, when the chemicals in&ol&ed are non-polar or

complex the results are &ery inaccurate. )n the separator processes designed, the

chemicals were all non-polar and %uite complex, ma*ing this e%uation rather

unsuita'le.

Problem background and methodology

2 process flow diagrams were designed on +spen H"" software. oth process

flow diagrams in&ol&ed mixers and separators. ue to this it was apparent 'oth

systems would ha&e mass and energy 'alances. To define any stream, 2 properties

must 'e *nown. +s the input temperature and compositions of the 3 chemicals were

*now aswell as the input pressure and the molar 'asis was set as

inlet/0*mol1hour, when all the unit operations were all added and heat was input

as re%uired, H"" automatically using the "#$ e%uation calculated the properties

of all streams.

(or the 0 separator process, the process flow diagram was set up as shown in figure


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0 'elow:

Figure 1: process flow diagram for 1 separator system

The inlet and inlet feed had the specified properties:

3.0

4.0

3.0

188

167

146

=

=

=

HC

HC

HC

x

x

x

The inlet pressure was 2 *a and the molar flow was set as 0*ol1hr. 4nergy

was also added as an inlet to the separator in order to allow the separation to occur.

This separation occurs due to the differing 'oiling points of the three components to

'e separated. Hexane has a 'oiling point of 65o!, heptane has a 'oiling point of

5o! and octane has a 'oiling point of 027o! 849H#"T, 23;.


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The composition and properties of the streams is shown in ta'le 0 'elow:

Stream Temperature

(oC

!eat flow (k"#hr $ass

flow

(kg#hr

%nlet feed 6 -2.06x0< 0.2x0=

$i&er outlet 6 -2.06x0< 0.2x0=

'apourproduct

023 -.5x06

=

iquid

product

023 -0.=x0< 722

The compositions of the streams is shown in figure >.


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(ollowing this, a 2 separator system was designed in the +spen H"" software.

"ensiti&ity anal

(ollowing this, the effects of small temperature changes of the li%uid product of

separator 2 was tested and the predicted effects on all other streams was analysed.

(igures ,?,# and " show the effects of increasing the temperature in 0o!

increments from 006-02o!. @ust a 0o! increase in temperature from 006o! to00


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49H#"T, 23 http:11www.elmhurst.edu1Cchm1&chem'oo*170hc'oilingpts.html