Various refinery processing schemes—such as FCC, coker, high olefin FCC and DCC—produce C3 and lighter components that are often rejected to the refinery fuel gas system. CB&I’s Low Pressure Recovery (LPR) technology is a highly-efficient, low-cost and inherently safe process for the recovery of ethylene, propylene, ethane and propane from these and other refinery off-gas streams. The technology upgrades these off-gas streams from fuel value to valuable olefins products. The LPR process can typically receive the off-gas feed at refinery battery limit pressure. Impurities are removed by fixed bed absorption and caustic or water wash prior to fractionation and recovery of the principal products. The process can be used in a stand-alone unit or it can be integrated with the recovery section of a new or existing ethylene plant. It is typically economic when used to recover the C3 and lighter materials on streams that contain a minimum of 30 kta of ethylene, ethane, propylene and propane.
The Low Pressure Recovery (LPR) process typically can receive the off-gas feed at refinery battery limit pressure. This eliminates the need for feed gas compression, thus lowering investment, operating costs, maintenance costs and improving reliability. Low temperature separation is avoided by the use of absorption technology. This provides olefins recovery above 99% at temperatures well above the point where NOx and NOx gums can deposit, which can lead to significant safety concerns. The unique and patented flow scheme is inherently safe since it employs the absorption sequence, thus avoiding low operating temperatures that otherwise would be required to achieve competitive olefins recovery. A patented, mixed refrigeration system provides all the refrigeration requirements, using a single refrigeration system instead of two or more systems as required with conventional technology. This saves capital investment, improves reliability and lowers maintenance costs. The LPR process has the capability to handle a broad range of feed compositions, not only from various refinery processing schemes, but also as the compositions vary with changes in refinery feeds or operating conditions.