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Chemical Technology • April 2016
PETROCHEMICALS
heater, limited throughput when the fired heater becomes
duty limited, or earlier shutdown for heat exchanger clean-
ing. All these negatively impact the profitability of the refin-
ery. Traditional manual heat exchanger fouling monitoring
with limited data and Excel spreadsheets does not always
catch which crude blends are incompatible, thus the same
condition for accelerated fouling can be repeated in the
future. It should also be noted that the percentage of crude
oils blended will have an impact on crude incompatibilities.
For example, an 80-20 blend with 20 % tight oil may not be
enough to see accelerated fouling, whereas a 70-30 blend
may be unstable and have additional unwanted fouling.
For the US, the Energy Information Administration (EIA)
expanded its monthly reporting of crude oil production with
new data on API gravity. What was so interesting was that for
the first nine months of 2015, most (50,8 %) of the crude
oil produced in the Lower 48 states were light oils with an
API gravity above 40 degrees (see Figure 2). The largest
share of production was in the 40,1 to 45 degree API grav-
ity range. Production increases over the past several years
in the Bakken, Permian Basin, and Eagle Ford formations
account for almost all recent growth in US crude oil output.
These low-permeability (tight oil) formations are producing
mostly light crude oils.
For the United States gulf coast, there was a major
investment in refineries to process heavier and sour crude
oils from sources such as Venezuela and Canada. This up-
grade investment in refineries was done prior to technology
advancements and the shale boom that has taken place in
the United States over the past several years. Unfortunately,
tight oil is not heavy or sour, so this creates a mismatch
in crude oil properties required for refineries upgraded to
handle heavier and sour crudes.
Another noticeable change is the crude unit cold section
pre-heat exchangers prior to the desalter. When operating
with one crude oil or a stable crude oil blend, fouling occurs
primarily in the hot section downstream of the desalter
and not the cold section. Because of this, the cold section
exchangers typically have minimal process measurements
like temperatures and pressures in and out of each bundle
for monitoring heat exchanger fouling. But tight oils have
paraffin waxes and significant quantities of filterable solids
(as much as 200 pounds (±90 kg) per thousand barrels)
that are fouling the cold section heat exchangers. Refin-
ers are now beginning to monitor these heat exchangers
more closely and work with both automation and chemical
companies to mitigate abnormal and accelerated fouling.
Today, refiners are also installing WirelessHART (IEC
62591) temperature and pressure measurements around
all crude unit pre-heat exchanger bundles and implement-
ing predictive analytic software applications to monitor and
analyse heat exchanger performance and minimise energy