PROFITABLY RECOVER REFINERY BY-PRODUCT NGLS, HYDROGEN AND ETHYLENE/PROPYLENE

摘要

Refineries have long been dealing with constantly changing market conditions. Currently,reduced domestic gasoline consumption, required ethanol blending, improved vehicle miles per gallonand more stringent fuel quality specifications have exacerbated the situation. Capturing opportunities toimprove margins will be crucial for survival and sustained profitability.Over decades of operation, refinery fuel gas systems have become the repository for purge gasesfrom Fluidized Catalytic Cracking, Delayed Coking, Catalytic Reforming, Hydrotreating,Hydrocracking and other process units. Figure 1 illustrates the various sources of hydrocarbon offgasand hydrogen purge streams in a typical refinery. Flare gas recovery systems also contribute to thebuild-up of non-methane components in refinery fuel gas. Hydrogen concentrations of 50 volume percent (and higher) are not unusual. Segregating fuel gas blending streams and extracting hydrogen, NGLsand ethylene/propylene provides a moderate capital cost route to improved profitability, triggered by the"perfect storm" conditions of low natural gas cost (to replace the heating value of extracted gases) andhigher values for recovered components. Hydrogen recovery and purification avoids costs of onsitehydrogen manufacture or import from area pipelines. Capital costs vary widely, dependent on refinerysize / complexity and scope of targeted component recoveries. While there is no "typical" recoveryproject, case study has shown such projects have attractive economics with payback from 1 to 3 years.Capital costs ranged from less than $5 million to approximately $100 million.Technology strategies for extraction and purification include cryogenic, pressure swingadsorption (PSA), semi-permeable membranes, compression and gas treating. BHTS has developedoptimized configurations utilizing a combination of technologies to meet a refiner's specific recoveryand purity targets.An initial screening study provides in-depth understanding of the current operation and identifiesopportunities for segregation, extraction, treating and purification of hydrogen, NGLs and olefinfractions of various streams connected to the fuel gas system. This is followed by a comprehensiveanalysis which includes capital & operating cost estimating, equipment layout / constructability analysis,piping changes and utility / offsites impacts.