Abstract
Off-gas from refining and petrochemical facilities often contains significant quantities of valuable natural gas liquids (NGL) and olefins. The composition and pressure of these off-gas streams is commonly much different than conventional natural gases and presents unique challenges.
While many gas processing technologies exist, most were developed for high-pressure natural gas applications. High hydrogen content often found in off-gases can reduce the effectiveness of these traditional processes. Further, certain trace components can require other considerations that are not common in natural gas processing facilities. Nitrogen oxides (NOx) that are often contained in off-gas streams can solidify and accumulate within the cryogenic plant. NOx, especially nitrogen trioxide (N2O3), are considered hazardous; limiting the minimum operating temperature of the plant can reduce the risk of accumulation. For conventional technologies, this temperature limitation can significantly reduce the recovery of valuable NGL.
Single mixed refrigerant (SMR) processes have been used for liquefied natural gas (LNG) liquefaction in numerous facilities dating back to the 1970s. A new process configuration was recently developed for an off-gas processing plant that incorporates an SMR system. The patent-pending process provides several advantages for NGL recovery from refinery or petrochemical off-gas compared to conventional processes, including the flexibility to accommodate a wide range of feed gas compositions and fluctuations in feed rate that are common in off-gas applications.
In addition to a detailed description of the process configuration, this paper presents the features of the SMR-based process and compares its performance to conventional technologies for off-gas processing. A case study is provided that illustrates the advantages of SMR over conventional processes.
