Petroleum and Coal Products, Refineries Industry Terminology

API gravity

A measure (in degrees API) of a petroleum liquid’s density relative to water; higher API indicates a lighter, less dense fluid. Used to classify crude oils and predict yields and processing difficulty.

We prefer crudes above 32° API to maximize light product yields.; Blend to 29° API to stay within the unit’s heater duty limit.; The assay shows 20° API, so expect high resid output.

Atmospheric distillation unit (ADU)

The refinery’s primary fractionation column that separates crude oil into boiling-range fractions at near-atmospheric pressure (e.g., naphtha, kerosene, gas oils, atmospheric resid). Sets the front end of the product slate.

The ADU overheads are routing to the naphtha stabilizer.; Raise the ADU cut point to shift kerosene into diesel.; ADU bottlenecking is limiting crude throughput.

Barrel (bbl)

Standard volume unit in the oil industry equal to 42 U.S. gallons (about 159 liters). Used for crude runs, product volumes, and trading.

The refinery runs 250,000 bbl/d.; We sold 500,000 barrels of RBOB for August delivery.; Unit yield is 20 bbl gasoline per 100 bbl crude.

Benzene, Toluene, Xylenes (BTX)

Key aromatic hydrocarbons commonly produced in reformers and aromatics complexes. High-octane gasoline components and petrochemical feedstocks subject to toxicity and spec limits (especially benzene).

Reformer aromatics (BTX) feed the petrochemical complex.; Benzene limits constrain our reformate pool.; Para-xylene margins drive CCR severity.

Catalytic cracking (FCC)

A process (typically fluid catalytic cracking) that cracks heavy gas oils into lighter products like gasoline and LPG over a solid catalyst. Major source of gasoline range molecules and propylene.

Shift VGO to the FCC to lift gasoline yield.; High delta coke is pushing regenerator temperatures.; Olefinicity of FCC naphtha affects RVP and octane.

Crude assay

A comprehensive lab characterization of a crude oil (distillation profile, properties, contaminants, yields). Essential for planning, pricing, and unit operability assessments.

The assay shows high CCR and metals—tough for the VDU and FCC.; We need a full assay to price this opportunity crude.; Assay TBP data drives LP planning results.

Delayed coker

A thermal cracking unit that converts vacuum resid into lighter products (naphtha, gas oils) and petroleum coke by long-residence-time cracking in drums. Increases light product yield from heavy feeds.

Run more resid through the coker to debottleneck the VDU.; Shot coke formation is tied to feed asphaltenes.; Coker naphtha needs hydrotreating before blending.

Desalter

Equipment upstream of the ADU that removes salts, water, and fine solids from crude oil using electrostatic coalescence and wash water. Protects exchangers, towers, and reduces corrosion/fouling.

Raise wash water to cut salt below 2 PTB.; Poor desalting is causing overhead corrosion.; Opportunity crudes require two-stage desalting.

EIA (Energy Information Administration)

U.S. government agency that publishes energy data, forecasts, and analysis (production, inventories, demand, prices). Widely used for market intelligence.

EIA weekly stats show gasoline stocks rising.; We benchmark runs against EIA PADD data.; Use EIA price series for crack spread analysis.

Energy Intensity Index (EII)

A benchmarking metric (often from Solomon Associates) that measures a refinery’s energy efficiency relative to a standard. Lower EII indicates better energy performance.

Our EII improved 3 points after the furnace revamp.; Target the Solomon EII median by 2026.; Hydrogen optimization is key to lowering EII.

Feedstock

Any raw material fed to a process unit (e.g., crude oil, VGO, naphtha). Composition and properties determine yields, operating conditions, and product quality.

Switching to heavier VGO feed changes FCC severity.; Isom unit feed must be low in sulfur and benzene.; LPG feed variability is impacting alkylation quality.

Flare system

Safety system that combusts excess hydrocarbons during upsets, startups, or maintenance to prevent overpressure and releases. Subject to emissions and reporting requirements.

Minimize flaring during the unit trip.; SOx limits apply to the main stack and flare.; Implement flare gas recovery to cut emissions.

Gasoline blending (RBOB/CBOB)

The controlled mixing of blendstocks to meet grade specifications for reformulated (RBOB) or conventional (CBOB) gasoline. Balances octane, RVP, sulfur, aromatics, and other specs.

Blend RBOB to 7.0 psi RVP for summer spec.; Too much reformate raises benzene—watch the cap.; Optimize octane giveaway in the blend model.

Gross Refining Margin (GRM)

The difference between the value of products produced and the cost of crude processed, usually expressed per barrel. A key profitability indicator before energy and operating costs.

GRM expanded to $12/bbl on stronger distillate cracks.; Hedging stabilized quarterly GRM.; Unit downtime compressed GRM despite favorable cracks.

Hydrocracking

A catalytic process that cracks and hydrogenates heavy gas oils into lighter products (jet, diesel, naphtha) using high-pressure hydrogen and bifunctional catalysts. Produces clean, high-quality fuels.

Run mild hydrocracking to maximize distillate yields.; Catalyst activity decline is limiting conversion.; We’re co-processing bio-feeds in the hydrocracker.

Hydrodesulfurization (HDS)

Catalytic removal of sulfur from petroleum streams using hydrogen over CoMo/NiMo catalysts. Essential for meeting low-sulfur fuel regulations and protecting downstream catalysts.

ULSD spec requires deep HDS.; HDS reactor ΔT indicates exotherm health.; Nitrogen in feed inhibits HDS activity.

Integrity operating windows (IOWs)

Documented limits on process variables (e.g., temperature, pressure, chemistry) that, if exceeded, could damage equipment integrity. Part of mechanical integrity and risk management.

Stay within IOWs for chloride and pH to prevent corrosion.; Exceeding temperature IOWs triggers an MOC.; We updated IOWs after the metallurgy review.

Isomerization

A catalytic process that rearranges straight-chain paraffins into isomers with higher octane (typically C5/C6). Used to upgrade light naphtha for gasoline blending.

Isom raises light naphtha octane to make more reformer cut.; Chloride balance is key to isomerization catalyst activity.; C5/C6 isomerization reduces RVP constraints.

Jet fuel (Jet A/A-1)

Middle-distillate aviation turbine fuel with tight specs on freeze point, smoke point, aromatics, and sulfur. Produced by kerosene hydrotreating and careful blending.

Freeze point and smoke point meet Jet A-1 specs.; Hydrotreating severity adjusted to hit jet aromatics limits.; Jet cracks widened versus diesel this month.

Joint venture (JV)

A business arrangement where two or more parties jointly own and operate an asset or entity, sharing risks, capital, and returns. Common in refining and petrochemical complexes.

The refinery is a 50:50 JV with a national oil company.; JV governance requires unanimous approval for major CAPEX.; The JV partners share crude sourcing synergies.

Kerosene

A middle distillate fraction from crude distillation used for jet fuel and heating. Properties include freeze point, smoke point, and sulfur.

Kerosene cut overlaps jet fuel—watch the cut point.; Kero hydrotreating reduces smoke point issues.; Seasonal demand shifts kerosene to diesel blending.

Key Performance Indicator (KPI)

Quantifiable metrics that track performance against targets (safety, reliability, energy, quality, profitability). Used for operations management and incentives.

Weekly KPIs include EII, on-stream factor, and giveaway.; Safety KPIs improved after the PSM refresh.; Tie manager bonuses to reliability KPIs.

Linear programming (LP model)

A mathematical optimization model used for refinery planning and blending. Maximizes margin subject to unit capacities, yields, specs, and logistics constraints.

LP suggests shifting VGO from FCC to hydrocracker.; Update LP yields with the new crude assay.; LP shows negative value for high-RVP components.

Liquefied Petroleum Gas (LPG)

A mixture of light hydrocarbons (mainly propane and butane) stored under pressure as a liquid. Used as fuel, petrochemical feed, and gasoline blending component.

FCC LPG propylene content impacts alkylation feed.; Winter demand lifts LPG prices.; VRU helps capture LPG from storage losses.

Material balance

Accounting for all inputs, outputs, and accumulations of mass in a process or unit. Fundamental for troubleshooting, loss accounting, and performance monitoring.

The hydrocracker material balance is off—check meters.; Conduct a unit mass balance after the turnaround.; Losses show up as negative material balance closure.

Merox process

A catalytic sweetening process that oxidizes mercaptans to disulfides in light streams (e.g., LPG, kerosene), reducing odor and improving product quality.

Treat kerosene in Merox to meet mercaptan limits.; Spent caustic from Merox needs proper disposal.; Merox unit capacity is constraining jet production.

Naphtha

A light distillation cut used as gasoline blendstock and reformer feed. Split into light/heavy and often hydrotreated to remove sulfur and nitrogen.

Heavy naphtha to the reformer; light naphtha to isom.; Naphtha RVP is too high for summer spec blending.; Metal content in naphtha poisons reformer catalysts.

Nelson Complexity Index (NCI)

A measure of refinery complexity relative to a simple crude distillation unit. Higher NCI indicates more secondary conversion capacity and product flexibility.

A 12+ NCI signals deep conversion capability.; Upgrading with a coker increases NCI and margins.; Peers with higher NCI outperformed in heavy crude markets.

Octane number (RON/MON)

Indices of gasoline’s resistance to knock: Research Octane Number (RON) and Motor Octane Number (MON). Used to set gasoline grades and blending strategies.

Boost pool octane with more reformate and alkylate.; RON-MON sensitivity affects drivability.; Avoid octane giveaway in premium blends.

OPEX (Operating Expenditures)

Recurring costs to operate and maintain facilities (labor, energy, chemicals, maintenance). Distinct from capital expenditures (CAPEX).

Hydrogen costs dominate refining OPEX.; Turnaround deferrals lower OPEX but raise risk.; Energy efficiency projects cut OPEX by 5%.

P&ID (Piping and Instrumentation Diagram)

Detailed engineering drawings that show process equipment, piping, valves, and instrumentation. Foundation for operations, safety reviews, and maintenance.

Verify valve tags against the P&ID before startup.; MOC requires updating affected P&IDs.; HAZOP references the latest P&IDs.

PSM (Process Safety Management)

A structured management system to prevent catastrophic releases of hazardous chemicals. Encompasses elements like MOC, operating procedures, training, and incident investigation.

PSM audit found gaps in mechanical integrity.; MOC is a core PSM element.; Strengthen PSM around high-pressure hydrogen units.

Quality giveaway

Over-delivery of product quality versus the minimum spec (e.g., blending to higher octane or lower sulfur than required). A hidden cost that reduces margin.

We’re giving away 1 RON—tighten the blend.; Sulfur giveaway in ULSD is costing margin.; Reduce vapor pressure giveaway to reclaim value.

Quantitative risk assessment (QRA)

A probabilistic analysis of process safety risks that quantifies frequencies and consequences of incidents. Used for design decisions, siting, and risk mitigation.

QRA supports siting of the new hydrogen unit.; Update QRA after the storage expansion.; QRA results drive emergency response planning.

Reformulated gasoline (RFG)

Gasoline formulated to reduce emissions in designated areas, with limits on benzene, RVP, sulfur, and often oxygenate requirements. Regulated under U.S. EPA programs.

RFG requires benzene and RVP controls.; EPA RFG regions change seasonal specs.; Blend RFG with oxygenates per local regs.

RVP (Reid Vapor Pressure)

A measure of gasoline volatility at 100°F (37.8°C). Critical for controlling evaporative emissions and drivability; subject to seasonal and regional limits.

Summer RVP caps at 7.0 psi in this market.; High pentane content raises pool RVP.; RVP waiver applies with ethanol blending.

Scope 1, 2, 3 emissions

Greenhouse gas accounting categories: Scope 1 (direct facility emissions), Scope 2 (purchased energy), Scope 3 (value chain, including product use). Used for ESG reporting and targets.

We’re targeting Scope 1 and 2 reductions via energy projects.; Scope 3 depends on product use and logistics.; Disclose all scopes in the sustainability report.

Sulfur recovery unit (Claus process)

Converts H2S from amine/acid gas into elemental sulfur via thermal and catalytic stages (Claus), often with tail gas treating. Ensures compliance with sulfur emissions and product specs.

SRU capacity limits crude sulfur intake.; Tail gas treating improved overall sulfur recovery.; SRU outages constrain HDS severity.

Tank farm

A collection of storage tanks for crude, intermediates, and products, including associated pumps and piping. Critical for scheduling, blending, and logistics.

Floating-roof tanks reduce breathing losses.; Tankage limits force product sales timing.; Inspect seals per the tank integrity program.

Turnaround (TAR)

A planned shutdown for inspection, maintenance, and upgrades. Major events affecting availability, CAPEX/OPEX, and reliability for subsequent runs.

The FCC TAR will tie in the new regenerator.; Extend run length to defer the next turnaround.; Scope creep is inflating TAR costs.

ULSD (Ultra-Low Sulfur Diesel)

Diesel fuel with very low sulfur content (typically ≤15 ppm in the U.S.). Requires severe hydrotreating and careful blending to meet cold flow and lubricity specs.

ULSD spec is 10–15 ppm sulfur depending on market.; Deep HDS and good cetane are key for ULSD.; Blend kerosene to adjust ULSD cold flow.

Utilities

Support systems such as steam, power, cooling water, instrument air, nitrogen, and hydrogen. Essential enablers that often limit capacity and efficiency.

Steam balance constrains hydrotreater throughput.; Power reliability impacts critical compressors.; Cooling water temperature drives condenser performance.

Vacuum distillation unit (VDU)

Separates atmospheric resid under vacuum to produce vacuum gas oils and vacuum resid, reducing thermal cracking. Supplies feeds to FCC, hydrocrackers, and cokers.

VDU bottoms feed the coker.; High flash zone temperature improves VGO recovery.; Overflash is fouling the wash section.

Vapor recovery unit (VRU)

Equipment that captures and condenses or adsorbs hydrocarbon vapors (VOCs), typically from storage tanks and loading operations, to reduce emissions and product loss.

Install a VRU to capture tank farm VOCs.; VRU reduces product losses and emissions.; Loading rack VRU compliance testing is due.

Waste heat recovery

Capturing energy from hot process streams or flue gases (via exchangers, economizers) to reduce fuel consumption and emissions. Improves energy efficiency and margin.

Add an air preheater to boost furnace efficiency.; Pinch study identified WHR opportunities.; Recovering flue gas heat lowers EII.

Work permit (Permit to Work, PTW)

A formal system that authorizes and controls hazardous work (hot work, confined space, line breaking). Ensures hazards are identified and mitigated before work starts.

Confined space entry requires a PTW and gas test.; Hot work permit needed for this repair.; Verify isolations per the PTW procedure.

Xylenes (para-, ortho-, meta-)

Aromatic isomers produced in reformers/aromatics plants. Para-xylene is a key petrochemical for PTA/polyester; xylenes also influence gasoline octane and aromatics specs.

PX margins justify reformer severity increase.; Xylene isomerization boosts para-xylene yield.; Xylene content affects gasoline aromatics limits.

Yield optimization

Adjusting operations, cut points, routing, and blending to maximize product value while meeting constraints. Driven by LP models, unit economics, and market cracks.

LP suggests re-cutting the ADU to lift diesel yield.; Catalyst change-out aimed at jet yield maximization.; Blend optimization reduced octane giveaway and improved yields.

Zero routine flaring

A commitment/policy to eliminate planned, continuous flaring of associated gas during normal operations, focusing flaring only on safety-related upsets. Reduces emissions and product loss.

Design the new unit to meet zero routine flaring goals.; Flare gas recovery helps achieve zero routine flaring.; Implement operational discipline to avoid routine flares.

Zone classification (hazardous areas)

Designation of areas with potential explosive atmospheres (e.g., IEC Zones 0/1/2 or NEC Class/Division). Guides equipment selection and electrical design to manage ignition risks.

This pump is in Zone 2; use suitable electrical equipment.; Hazardous area classification updated after the process change.; Follow Zone 1 requirements near the vapor space.