not normalised for flow. After the start-up of the solids and emulsion separation system, the operators were able to raise the flow rate through the exchanger because the dP was no longer rising. When the flow rate is increased, the heat exchanger dP will rise due to the increased flow. In addition, there are fluctuations in the flow rate during routine operation.
Since differential pressure is related to flow, and the flow through the unit has increased and fluctuated, the true trend in differential pressure is a significant downward decline when normalised for flow, as shown in Figure 4 . The graph of the dP normalised negates the effect of the flow rate increase and shows that the dP consistently dropped over the entire time period and eventually levelled out. The system has not experienced heat exchanger fouling or dP increase since the start of the Torsep solid and emulsion separator operation. Hydrocarbon recovery Hydrocarbon recovery can be determined by plotting the level of the liquid-liquid interface in the boot alongside the percentage open of the boot level control valve (the ‘dump’ valve). These graphs *1 show the boot interface level as a line
Figure 2 Installation at the refinery
Impact on heat exchanger fouling As discussed previously, the pressure drop (dP) across the heat exchanger in the sour water system continues to rise until the operators are forced to shut down and clean the exchanger. The blue and green lines shown in Figure 3 represent the dP signals in units of inch water column and PSI. Data provided by the refinery shows that the constant upward trend in the sour water exchanger’s dP stopped within minutes of bringing the system online. Following the start- up, the upward trend stopped and even slightly reversed. The dP has remained nearly constant since the start-up, and the refiner has not had to shut down to clean the heat exchanger. It is to be pointed out that the dP of the heat exchanger over time, as shown in Figure 3, is
F/E Inlet pressure (psig)
SWS B F/E dP (psi)
SWS A F/E (inWC)
Endur dP (inWC)
System started
Envision dP (inWC)
Figure 3 Operating data
Refining India
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