UGDC Approach to mitigate the undesired drawbacks of lean gases on the NGL extraction process

摘要

Port Said NGL plant owned by united gas Derivatives Company (UGDC) was designed toproduce propane, LPG and DNG by using Ortloff IOR for propane recovery enhancement.Unfortunately, the current feed gas became leaner than design feed gas composition which inturn dramatically reduced the liquid flow in the NGL extraction area and accordinglynegatively affected in the propane recovery and causing high differential temperature over thedesign limit between the cold & warm streams at inlet of the gas liquid heat exchanger whichaffect the integrity of the mentioned heat exchanger.Three proposals evaluated and studied to mitigate the problem1. Reinjection of liquid product (propane, Mixed NGL, Condensate or LPG) from thefractionation area into the feed gas with the aim to eliminate thermal stresses in gasliquid cold box and maximize the plant C3 recovery and hence the plant productivity.Various simulation calculations performed for the three mentioned streams, resultsshow improvement in the temperature difference between adjacent layers of gas liquidheat exchanger as well as improvement in the temperature profile of the demethanizertrays which is reflected on propane % recovery and productivity however the mostgain is from NGL scenario.2. Using the same liquid stream from absorber bottom pump for feed gas cool down inthe G/L cold box bypassing the other liquid stream directly to the demethanizer forreducing the temperature difference between adjacent layers at the mid-point of theG/L cold box as well as keeping the propane % recovery at the same level.3. Liquid re-arrangement for Gas/Liquid exchanger by taking split stream from inletpass C (absorber bottom stream) to inlet pass B (Bottom of expander feed separator)for increasing liquid flow into pass B which improves the temperature differencebetween adjacent layers in the G/L cold box as well as keeping propane % recovery atthe same level.