(52c) Practical Process Integration Retrofit Part 3. Path Analysis

Practical Process Integration Retrofit

Part 3. Path Analysis

  G.T.Polley

The
concept of transferring heat along paths was first suggested by Dhole [1]. It
was subsequently investigated by Adiarso [2] and Van Reisen [3,4]. It forms the
basis of a technique known as ?Network Pinch? introduced by Zhu & Asante
[5].

When
using path analysis the engineer concentrates on minimising the number of
changes that are made to the existing network structure for such changes
generally involve quite large capital investment.

The
identification of existing heat recovery paths and possible new paths is
usually quite straight forward and does not require the use of special software.

The
technique should not be used in isolation. It is worth undertaking a
cross-pinch analysis to establish if structural change is justified. For
instance when software employing the network pinch analysis was applied to a
large problem Al Riyami et al [6], it failed to identify simple energy saving
opportunities associated with re-boilers positioned well below the pinch [7].

Procedure

Example:
Increased Heat Recovery in Pre-Heat Train

Features
to be Observed in Path Analysis

Bridges

Blocks

Fixed Loads

References

[1] 
V.R.Dhole, Private Communication, UMIST, 1990

[2] 
Adiarso, ?Application of Problem Decomposition in Process Integration
Retrofit?, M.Sc. Dissertation, UMIST, 1993

[3]
Van Reisen J.L.B., Grievink J., Polley G.T. & Verheijen P.J.T. ?The
placement of two-stream and multi-stream heat-exchangers in an existing network
through path analysis?, Comp.& Chem. Engng., 1995, 19,S143-S148

[4]
Van Reisen J.L.B., Polley G.T. & Verheijen P.J.T. ?Structural Targeting for
Heat Integration Retrofit?, Appl. Thermal Engng. 1998, 18(5), 283-294

[5]
Asante N.D.K. & Zhu X.X. ?An automated approach for heat exchanger network
retrofit featuring minimal topology modifications?, Comp.& Chem. Engng.,
1996, 20,S7-S12

[6]
Al Riyami B.A., Klemes J. & Perry S.,
?Heat integration retrofit analysis of a heat exchanger network of a fluid
catalytic cracking plant?, Appl.Thermal Engng. 2001, 21, 1449-1487

[7]
Polley G.T. & Kumana J.D. ?Energy Saving Retrofit of FCC Plant?,       NPRA
 Annual Meeting, March 2007, San Antonio, Texas