Refiners are turning cracking by‑products into power, hydrogen, and profit

Cracking units don’t just make gasoline and diesel; they spin off a light “fuel gas” and, in heavier schemes, solid petroleum coke. Both by‑products are increasingly central to how refineries run their own utilities and balance hydrogen demand.

One case study in Nigeria found fuel gas averaged about 9% of the refinery’s fuel‑energy mix between 2000 and 2011 (ResearchGate). And modern turbines can burn very lean refinery gas — down to roughly 235 Btu/ft³ (British thermal units per cubic foot, a measure of heating value) — to generate 3–50 MW of power or combined heat and power (CHP) from off‑gas (Solar Turbines).

Petroleum coke, meanwhile, rarely goes to waste. Roughly 80% of global output is burned as fuel in energy‑intensive industries, chiefly cement and power (CW Group), and some kilns have proven it can be taken even further.

Refinery fuel gas: composition and duty

Cracking units — particularly FCC (fluid catalytic cracking) and cokers — generate a light off‑gas rich in C1–C4 hydrocarbons, hydrogen (H₂), carbon monoxide (CO), and similar species. Because its heating value is low (often a few hundred Btu/ft³), it’s typically unsuitable for sale as product but valuable on site as fuel. In practice, “fuel gas is generally used as fuel in various process heaters and steam boilers in the refinery” (Oil & Gas Journal).

Blended refinery gas also runs gas turbines; OEMs cite capability to burn fuel as lean as ~235 Btu/ft³ and deliver 3–50 MW in power/CHP configurations (Solar Turbines). Using fuel gas for cogeneration — producing on‑site power and steam — can markedly improve energy efficiency, displace purchased fuel or electricity, and reduce greenhouse‑gas emissions (Solar Turbines).

Because fuel gas is “routinely cleaned/blended,” many sites pair gas cleanup with amine treatment; amine solvent systems for CO₂/H₂S removal, such as an amine solvent, and accurate chemical metering via a dosing pump can be integrated upstream of heaters, boilers, or turbines as part of the fuel‑gas balance.

Turning off‑gas into hydrogen supply

Hydrogen‑rich upgrading (hydrocracking, hydrotreaters, cokers) tends to increase fuel‑gas output at the same time refiners face rising H₂ demand. Studies recommend routing fuel gas — and LPG (liquefied petroleum gas) by‑products — into steam reforming to meet that demand (Oil & Gas Journal).

One review notes that today’s “refiners faced with increasing hydrogen demand” should “consider producing additional hydrogen from fuel‑gas streams” (Oil & Gas Journal). Heavier crude processing can produce excess fuel gas and can “occasionally limit crude processing” if not used efficiently (Oil & Gas Journal). Conversely, integrating fuel gas into a combined‑cycle or IGCC (Integrated Gasification Combined Cycle) scheme — fueling gas turbines and HRSGs (heat recovery steam generators) — can turn otherwise “waste” off‑gas into reliable heat and power.

In short, leveraging fuel gas on‑site — via optimized mixing systems, turbine/boiler burning, and even reforming for H₂ — can supply 5–15% or more of a refinery’s energy needs (ResearchGate; Solar Turbines), while reducing flaring and external fuel purchases.

Petroleum coke: yields and quality

Heavier cracking, especially delayed coking, yields solid petroleum coke (“petcoke”), a high‑carbon residue (~90% carbon). It is produced at roughly 31 kg per tonne of crude processed (ScienceDirect), implying on the order of 70 million tonnes per year globally in 2015 (ScienceDirect).

Petcoke is often high in sulfur (5–7 wt%) and metals (nickel and vanadium up to hundreds of ppm), which make direct combustion challenging due to ash fouling and emissions (ScienceDirect; ScienceDirect).

Beneficial reuse in kilns and power

Rather than landfilling, refineries almost exclusively seek beneficial reuse. About 80% of worldwide petcoke output is burned as fuel in energy‑intensive industries, chiefly cement and power plants (CW Group). Cement kilns are well‑suited to high‑carbon, high‑sulfur fuels; for example, Nesher Cement’s Rabigh plant was designed to fire 80% of its energy from petroleum coke, with operational reports achieving stable 100% petcoke firing after adjusting combustion parameters (Scribd). Sulfur is managed via kiln scrubbers or blending.

Petcoke can also substitute for coal in power plants or be gasified. IGCC units can convert petcoke into syngas for gas turbines, yielding electricity and high‑pressure steam for in‑plant use — steam that drives compressors, pumps, or provides process heat (ScienceDirect). Even when co‑fired in conventional boilers, petcoke can supply base‑load power, though high metals in ash (Ni, V) cause corrosion and end‑of‑pipe pollutants (ScienceDirect). Gasification/IGCC partially alleviates this via gas cleanup. In practice, some refineries and utilities burn petcoke‑coal mixtures or operate dedicated petcoke boilers to free up natural gas.

Crushed petcoke stockpiles must prevent dust emissions, as fugitive dust can cause local air pollution. Many operators turn to targeted dust‑control chemistry; where applicable, a coal dust suppressant approach is often adapted for petcoke handling yards.

Calcining, handling, and disposal

A portion of petcoke is calcined at about 1300°C to make CPC (calcined petroleum coke) for aluminum‑smelter anodes — a common refinery by‑product market, typically separate from disposal. If reuse options are limited, coke is handled as a waste, usually as non‑hazardous industrial fuel rather than landfill. Spent FCC catalyst coke, however, is burned on the regenerator and rarely enters waste streams.

Under strict regulation, secure landfilling would likely be required given heavy metals, but this is uncommon because demand for coke as a cheap fuel remains strong (CW Group).

Energy balance and margins

Across the board, using refinery fuel gas for heaters, boilers, and turbines — and even reforming it for hydrogen — can supply roughly 5–15% or more of a refinery’s energy needs (ResearchGate; Solar Turbines). That reduces flaring and external fuel purchases, and it aligns with “generally used” practice for heaters and boilers (Oil & Gas Journal).

Sources and references

Industry studies and reports (Applied Petrochem. Res., Oil & Gas J.) and global analyses provide yield and usage data (ResearchGate; Oil & Gas Journal). Reuse statistics (e.g., 80% of petcoke burned in cement/power) are from market analyses (CW Group). Technical metrics (e.g., 31 kg coke/t‑crude) are from fuel‑analysis reviews (ScienceDirect; ScienceDirect). Inline citations identify all data and claims.