Investigation and Simulation of Replacement of Propane as Refrigerant in NGL Plant
Gas containing considerable amounts of liquefiable HC (ethane, propane and heavier) produces condensate upon cooling or compressing and cooling. If condensation would occur in the transportation, processing, or use of the gas, it may be better to remove the condensate at or near the wellhead. In some cases the potential NGL are sufficiently valuable to justify their recovery, quite apart from other considerations. Normally, condensate is fractionated into the NGL products in a central facility rather than in the field. Recovered condensate may have to be stabilized by partial removal of dissolved gaseous components to obtain a liquid product with low-enough vapor pressure to be transported safely. Obviously any cooling will induce condensation and yield NGL. Most common liquid recovery processes are compression
refrigeration, expansion across a turbine and expansion across a valve.
In this article five case studies are investigated. The technology that was used to perform the calculations was the process simulation programs HYSIS 3.01.We simulate a compression refrigeration cycle with propane as fluid work to decrease gas temperature, which gathering from the wells near the Ahvaz (south oil region of Iran), from 54.5ºC (130ºF) to -34.5ºC (-30ºF). Then change propane to ethane, n-butane, i-butane and mixture of isobutene and normal butane and evaluate results of these replacements. With comparing required rate of refrigerant, heat loads of compressors and heat exchangers, operating pressure can deduce propane is the best refrigerant to recovery of natural gas liquids in gas industry.