Determining Production Separator Operating Pressure

separator pressure effect on storage tank liquid recovery

Separator pressure effect on storage tank liquid recovery

High initial pressure is needed to obtain maximum liquid output in production separator. The incoming liquid stream may contains many light components. These light components will stay liquid in the separator and vapor in the storage tank if the initial pressure is too high. However, if the initial pressure is too low many of these components will vapor to gas phase and leave the separator through gas outlet.

The figure above showed this phenomenon. The partial pressure of a component determines its tendency to evaporate from the process stream. If the pressure inside the vessel is high then the partial pressure for the component will also be high and the component will stay liquid. As you can see in the chart, the liquid output flow rate will increase if the pressure increased. So we just have to increase the pressure as high as possible to obtain high production output, unfortunately not that simple.

The problem is, many of these components are methane, ethane, and propane which are lighter. These light components will leave the vessel on liquid form but it will vapor in the storage tank which has atmospheric pressure. So there is point that we call optimum point, if we go beyond that optimum point then there will be a decreasing in the storage tank by increasing the separator operating pressure.

1. Surface Production Operations, Ken Arnold and Maurice Stewart


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