Recovery of light olefins—typically ethylene, propylene or butylene—from offgases using reflux exchanger technology as part of a low-temperature recovery system (LTRS). Reflux exchanger technology can also be applied to ethylene chill trains and to NGL recovery from refinery and petrochemical offgases, as well as from natural gas.
Products: Olefins with a typical recovery of 99%. For NGL recovery: 95+% recovery of propane and 100% recovery of heavier hydrocarbons.
After removal of water and freezable components in the molecular sieves (1), the gas is partially liquefied in the plate-fin heat exchanger (2) and separated in the feed separator (3). The vapor formed passes upward through the passages of a refluxing plate-fin heat exchanger (4) where it is cooled and condensed. Condensed liquids flow counter currently to the gas down the heat exchanger passages and are fractionated before collecting in the feed separator. The resulting gas is then rewarmed and sent to product/fuel gas while the liquids collected are stabilized. Refrigeration (5) may be provided by a separate refrigeration cycle or by work expansion of the product/fuel gas. The choice of refrigeration scheme depends on both feed and product/fuel gas pressures.
Operating conditions: Typically, feed gas flows of up to 100,000 Sm3/h can be processed. Feed gas pressure is typically between 10 barg and 70 barg.
Economics: The PetroFlux process offers high recoveries and significant savings in refrigeration costs, giving attractive returns on investment. It has been used widely for plant debottlenecking and to make more effective use of existing refrigeration systems.
Licensor: Costain Oil, Gas & Process Ltd.