Chemical Technology April 2016

PETROCHEMICALS

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

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

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Chemical Technology • April 2016