(31c) Design of Compabloc Exchangers to Mitigate Refinery Fouling

Design of Compabloc
Exchangers to Mitigate Refinery Fouling

E. Tamakloe & G.T.Polley

Dept. of Chemical Engineering,
University of
Guanajuato

Welded plate heat exchangers (such as Compabloc^TM
units offered by Alfa Laval) are finding wide application in the oil and
process industries.

Quite complex flow arrangements can be used in such units.
For instance, the authors know of one case in which a hot stream flowed through
twelve passes whilst being matched against a cold stream that flowed through
just 3 passes.

It is also common to find that the physical properties of
the fluids being handled exhibit quite large changes between inlet and outlet
of the exchanger. This means that the individual film heat transfer
coefficients are different for each individual pass.

In this paper the authors describe how the performance of
such exchangers can be analysed.

Since, an important application of such exchangers is
improved heat recovery at the hot end of crude oil pre-heat trains,
analysis of fouling behaviour of such units is also addressed.

MODELLING BEHAVIOUR
OF A BASE CONFIGURATION

DEALING WITH VARIABLE
PROPERTIES

OVERALL ALGORITHM

FOULING IN WELDED
PLATE EXCHANGERS

EXAMPLE APPLICATION

CONCLUSIONS

In order to get good performance out of a welded plate heat
exchanger it is often necessary to use multiple passes. A range of possible
configurations is possible. Some of these configurations are complex.

The behaviour of multi-pass units has now been modelled. The
modelling has included consideration of the variation of physical properties
over the length of the exchanger.

The shear stresses developed in this type of exchanger can
be much greater than those possible in shell-and-tube heat exchangers. This has
led to interest in the application of this type of exchanger in crude oil
pre-heat trains.

Examination of monitoring data has indicated that fouling
models currently used to predict fouling rates in shell-and-tube heat
exchangers may also apply to welded plate exchangers. Consequently, such a
model has been incorporated into the modelling of welded plate exchanger
behaviour.

Examination of an example application has demonstrated the
importance of considering fouling behaviour during the design of this type of
heat exchanger.

REFERENCES

Colburn A. P. 1933, ?Mean Temperature difference and heat
transfer coefficient in liquid heat exchangers?, Ind. Eng. Chem. Vol 25 873-877

Kern D. Q. 1950, Process Heat Transfer,
McGraw-Hill, New York.

Polley G.T., Tamakloe
E. & Picon Nunez M. ?Models for chemical reaction
fouling?, paper presented at AIChE Spring Meeting,
Chicago, March, 2011

McCartney T. & Smith S. ?Advancements in large scale
application of ultrasonic cleaning in removal of refinery fouling?, 11^th
Annual Intnl. Conf. on Petroleum Phase Behaviour and
Fouling, June, 2010,
Jersey City

Yeap B.L., Wilson D.I., Polley G.T. & Pugh S.J. ?Mitigation of crude oil
refinery heat exchanger fouling through retrofits based on thermo-hydraulic
fouling models?, Trans.I.Chem.E.,2004,82A,53-71