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Fouling In Heat
Exchangers
The
retardation of heat transfer caused by fouling
in Heat Exchangers is the prime reason for the
increase in energy, maintenance, and operational
cost!
What
is Fouling?
Fouling is generally
defined as the accumulation of unwanted materials
on the surfaces of processing equipment. It
has been recognized as a nearly universal problem
in design and operation and affects the operation
of equipment in two ways:
-
The
fouling layer has a low thermal conductivity.
This increases the resistance to heat transfer
and reduces the effectiveness of heat exchangers
– increasing temperature
-
As
deposition occurs, the cross-sectional area
is reduced, which causes an increase in pressure
drop across the apparatus
Cost
Due to Fouling
Despite the enormous
costs associated with fouling, only very limited
research has been done on this subject. Reliable
knowledge of fouling economics is important
when evaluating the cost efficiency of various
mitigation strategies. The total fouling-related
cost can be broken down into four main areas:
-
Capital
expenditure, which includes excess surface
area (10-50%, with an average around 35%),
costs for stronger foundations, provisions
for extra space, increased transport and installation
costs.
-
Extra
fuel costs, which arise if fouling leads to
extra fuel burning in furnaces or boilers
or if more secondary energy such as electricity
or process steam is needed to overcome the
effects of fouling.
-
Production
losses during planned and unplanned plant
shutdowns due to fouling.
-
These
are often considered to be the main costs
of fouling and are very difficult to estimate.
According to
Pritchard and Thackery (Harwell Laboratories),
about 15% of the maintenance costs of a process
plant can be attributed to heat exchangers and
boilers, and of this, half is probably caused
by fouling.
Fouling can be very costly in refinery and petrochemical
plants since it increases fuel usage, results
in interrupted operation and production losses,
and increases maintenance costs. Panchal (Argonne
National Laboratory), based on the study of
Van Nostrand, re-estimated the energy and economic
penalties associated with heat exchanger fouling
for the US refineries, as more than $2 billion
per year. The maintenance costs in the USA were
revised because they have increased significantly
due to recent environmental regulations.
Typically, cleaning costs are in the range of
$40,000 to $50,000 per heat exchanger per cleaning.
Garrett-Price and Pritchard found that total
heat exchanger fouling costs for highly industrialised
countries such as the US and the UK are about
0.25% of the countries’ gross national
product (GNP). Steinhagen et al found that the
fouling costs for New Zealand are 0.15% of the
New Zealand GNP, which is less than for industrialised
countries. Using these percentages, Müller-Steinhagen
lists total fouling related costs for various
countries based on 1992 US$.
The
Perfect Solution To Your Water Scale Problems!
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Fouling
In Heat Exchangers
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