Sub-Product

Refinery Fuel Gas (RFG) means a gaseous mixture of methane, light hydrocarbons, hydrogen, and other miscellaneous species that is produced in the refining of crude oil and/or petrochemical processes and that is separated for use in boilers and process heaters throughout the refinery^[1]. 

On a dry basis, major components in RFG can consist of percent levels of numerous hydrocarbons (C₁-C₆⁺ , saturated and unsaturated), hydrogen (H₂), carbon oxides (CO and CO₂), nitrogen (N₂), and possibly some oxygen (O₂)^[1]. 

Saturated hydrocarbons in RFG come from catalytic reforming, hydrotreating, hydrocracking, and the like; unsaturates arise from such refining processes as catalytic cracking and coking^[1]. 

Hydrogen in RFG may vary from 10% up to about 60% if not separated for use in hydrotreating operations for sulfur removal from refinery feeds and products^[1]. 

RFG also contains various sulfur species, including hydrogen sulfide (H₂S) and mercaptans (RSH), at concentrations expressed in units of parts per million (ppm). The sulfur species originate from the organic sulfur compounds contained in the crude oil processed by the refinery^[1]. 

The typical specific gravity of refinery fuel gas is approximately 0.6, based on a composition of 30% hydrogen, 35% methane, and 35% ethane, with a calculated value of 0.58. However, variability exists, with some refineries having heavier compositions, potentially increasing specific gravity above 1. This aligns with industry context where RFG's heating value is similar to natural gas, reinforcing the 0.55 to 0.60 range^[2].

References

1. Kunz, 2009, Environmental Calculation - Appendix L, Combustion of Refinery Fuel Gas.
2. Grok 3 Deep Search, 11th Mar 2025, Prompt: "What is the typical specific gravity of refinery fuel gas?"