{"id":2432,"date":"2026-05-06T08:29:36","date_gmt":"2026-05-06T08:29:36","guid":{"rendered":"https:\/\/boshiya.com\/?p=2432"},"modified":"2026-05-06T08:52:05","modified_gmt":"2026-05-06T08:52:05","slug":"cat-cracker-operation-refinery","status":"publish","type":"post","link":"https:\/\/boshiya.com\/ja\/blog\/cat-cracker-operation-refinery\/","title":{"rendered":"\u30ad\u30e3\u30c3\u30c8\u30af\u30e9\u30c3\u30ab\u30fc\u3068\u306f FCC\u30e6\u30cb\u30c3\u30c8\u306e\u64cd\u4f5c&\u88fd\u6cb9\u6240\u30ac\u30a4\u30c9"},"content":{"rendered":"

How a Cat Cracker Works: The FCC Unit’s Role in Petroleum Refining<\/span><\/p>\n

\n

At its core, the FCC unit (also called a cat cracker) is the critical refinery unit that converts vacuum gas oil (VGO) \u2014 a heavy, low-value residue remaining after crude distillation \u2014 into high-octane gasoline, LPG, and diesel blending components a modern refinery needs to operate profitably. Known officially as a Fluid Catalytic Cracking unit, it employs a continuously circulating fluidized zeolite catalyst to crack hydrocarbons at high temperature inside a reactor, with the catalyst fired in the regenerator. For oil refinery equipment services<\/a> managers, the catalyst cracker can be one of the most heavily-maintained refinery units–something this guide discusses in some detail.<\/p>\n

<\/p>\n

Cat Cracker (FCC Unit) at a Glance: Quick Specs<\/h2>\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Parameter<\/th>\nTypical Value<\/th>\n<\/tr>\n<\/thead>\n
Unit type<\/td>\nFluid catalytic cracking (FCC)<\/td>\n<\/tr>\n
Typical capacity<\/td>\n20,000\u2013100,000+ bbl\/day<\/td>\n<\/tr>\n
Primary feedstock<\/td>\nVacuum gas oil (VGO), 340\u2013550\u00b0C fraction<\/td>\n<\/tr>\n
Feed preheat temperature<\/td>\n315\u2013430\u00b0C (600\u2013806\u00b0F)<\/td>\n<\/tr>\n
Riser outlet temperature (ROT)<\/td>\n510\u2013552\u00b0C (950\u20131,025\u00b0F)<\/td>\n<\/tr>\n
Reactor pressure<\/td>\n~1.72 bar (25 psi)<\/td>\n<\/tr>\n
Regenerator temperature<\/td>\n700\u2013760\u00b0C (1,290\u20131,400\u00b0F)<\/td>\n<\/tr>\n
Catalyst-to-oil ratio (C\/O)<\/td>\n4:1 to 8:1 (wt\/wt)<\/td>\n<\/tr>\n
Residence time in riser<\/td>\n2\u20134 seconds<\/td>\n<\/tr>\n
Typical turnaround interval<\/td>\n4\u20135 years (industry median: 4.5 yr)<\/td>\n<\/tr>\n
Primary product<\/td>\nHigh-octane gasoline\/naphtha (49\u201353 wt% of output)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

<\/p>\n

What Is a Cat Cracker? Definition, History, and Refinery Role<\/h2>\n

\"What<\/p>\n

A cat cracker is a refinery unit that incorporates a powdered zeolite catalyst to unusually heavily intentionally break apart, chemically change, primarily VGO into lighter, more valuable arrangements. Unlike the physical distillation of the oil into different fractions by boiling point, FCC is a chemical process that changes the assembly of individual molecules, as opposed to separating them. Primary products \u2014 high-octane gasoline, LPG, and light cycle oil \u2014 rank among the most valuable streams in a modern refinery.<\/p>\n

‘Cat’ is short for catalyst \u2014 the powdered (10\u2013150 micron diameter) zeolite material that breaks apart hydrocarbons at very high temperature without itself being consumed. ‘Fluid’ refers to those small particles being held airborne by hot vapors and steam, which forces them to behave like a liquid and circulate continuously between the cracking reactor and regenerator. This continuous cycling of catalyst is called fluidization, and has made the FCC unit form the most important innovation in the catalytic cracking process<\/p>\n

Important historical progressions: Eugne Houdry was the first engineer to provide proof-of-concept for installing a catalytic cracking unit using a zeolite catalyst in a commercial environment in 1936 at Socony-Vacuum’s refinery; it achieved a gasoline yield of just over 50%, vs approximately 25% of the thermal cracking pioneered at that time. Standard Oil of New Jersey’s Model I FCC \u2014 installed at Baton Rouge on 25 May 1942 and processing 13,000 bbl\/day \u2014 is regarded as the template for the modern FCC unit<\/p>\n

Today some 400 FCC units operate globally. As of 2023, the US accounted for 5.3 mn bbl\/d out of 15.9 mn bbl\/day total FCC capacity, with global capacity at 14.4 mn bbl\/d in 2022 (GlobalData) \u2014 forecast to reach 15.8 mn bbl\/d by 2026.<\/p>\n

\n

Popular misconception: FCC units are often confused with cokers or hydrocrackers. An FCC unit employing zeolite catalyst operates at low pressure (~ 1.7 bar) with re-circulating catalyst particles. A hydrocracker requires hydrogen to break down hydrocarbons and is operated at ultra-high pressure (~100-200 bar); a delayed coker operates at very high temperature in the absence of catalyst to thermally break down heavier visbroken hydrocarbons to lighter products.<\/p>\n<\/div>\n

<\/p>\n

Cat Cracker vs. Thermal Cracking: Why FCC Replaced Older Methods<\/h2>\n

\"Cat<\/p>\n

Prior to commercial development of fluid catalytic cracking, refiners used thermal cracking, or cracking using solely heat as a reactive agent. Thermal cracking is characterized by low gasoline yields (~25%), inferior octane quality, and relatively large residuals. Catalytic cracking’s economic efficiency was first demonstrated by the Houdry unit installed in 1937 at Sun Oil’s Marcus Hook refinery.<\/p>\n

This 12,000 bbl\/day unit produced nearly twice the gasoline yield with substantially higher octane requirement (TON). Today, refiners have three options for cracking based on feed stock, capital budget and product requirements,<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n
Feature<\/th>\nFCC (Cat Cracker)<\/th>\nThermal Cracking<\/th>\nHydrocracking<\/th>\n<\/tr>\n<\/thead>\n
Catalyst<\/td>\nZeolite (Y-type)<\/td>\nNone<\/td>\nNi\/Mo on alumina<\/td>\n<\/tr>\n
Operating temperature<\/td>\n510\u2013552\u00b0C<\/td>\n450\u2013600\u00b0C<\/td>\n330\u2013430\u00b0C<\/td>\n<\/tr>\n
Operating pressure<\/td>\nLow (~1.7 bar)<\/td>\nModerate<\/td>\nHigh (100\u2013200 bar)<\/td>\n<\/tr>\n
Gasoline yield<\/td>\n49\u201363 wt%<\/strong><\/td>\n~25 wt%<\/td>\n50\u201365 wt%<\/td>\n<\/tr>\n
Gasoline octane (RON)<\/td>\n89\u201394<\/td>\n~72\u201378<\/td>\n80\u201388<\/td>\n<\/tr>\n
Hydrogen required<\/td>\nNo<\/td>\nNo<\/td>\nYes (large H\u2082 plant)<\/td>\n<\/tr>\n
Coke yield<\/td>\n4\u20136 wt%<\/td>\nHigh<\/td>\nMinimal<\/td>\n<\/tr>\n
Capital cost<\/td>\nModerate<\/td>\nLow<\/td>\nVery high<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Decision guide: go to FCC if you have VGO feed, high gasoline is required and a hydrogen plant cannot be justified. go to hydro cracking if fluor sulfur\/metals are to high for direct FCC or when jet\/diesel are the goal.<\/p>\n

<\/p>\n

FCC Unit Design: Riser, Reactor, Regenerator, and Fractionator Explained<\/h2>\n

\"FCC<\/p>\n

What Are the Main Components of an FCC Unit?<\/h3>\n

Modern FCC units divide into four main sections. Each drives the continuous cycle of cracking and regeneration:<\/p>\n

    \n
  1. RiserA short tubular pipe 10-50 m, high where the whole catalytic cracking process takes place. The feedstock (315-430 C) is preheated and introduced at the bottom of the riser and there is introduced atomized in contact with hot regenerated catalyst( 700 C). The rapid vaporization occurs directly follows this process.Cracking reactions complete within 2\u20134 seconds as vaporized feedstock rises through the riser; this short residence time is by design, preventing over-cracking of gasoline-range molecules into dry gas (methane, hydrogen, CO).<\/li>\n
  2. Reactor Vessel\u2014 receives the riser effluent (cracked vapors +spent catalyst) at ~ 535 C and 1.72 bar. Two-stage cyclones remove catalyst out of the cracked vapor. Steam stripping section\u2022 below the cyclones stripper any remaining hydrocarbon remaining in the spent catalyst to recover value product and protect from regenerator as efficiently.<\/li>\n
  3. Regenerator- accepts spent catalyst containing 0.8-1.2 wt % coke. Preheated air supplied to regenerator burns coke at 700-760 C (2.41 bar), present in catalyst- high temperature required for this highly exothermic reaction is main source of heat for FCC unit, and due to high temperature, core cracking feed reactions are endothermic. Due to large catalyst inventory (~150 tonnes) and high circulation rates (~5 kg of catalyst for every kg of feedstock), FCC unit is thermally self-sustaining.<\/li>\n
  4. Main fractionator\u2014Cracked vapors from the reactor (~535C) are introduced into the main fractionator. The main fractionator separates the vapors into FCC naphtha (gasoline blendstock), light cycle oil (LCO, diesel blendstock), heavy cycle oil (HCO), and clarified slurry oil through distillation. The light offgas is released from the top of the main fractionator toward the downstream gas concentration unit for LPG recovery.<\/li>\n<\/ol>\n
    \n

    Engineering Note – Riser design: The regenerator will run about 0.7 bar excess pressure of the reactor to induce gravity \/ pressure driven catalyst flow. Two mechanical production designs: Stacked (reactor over regenerator – less plot area) and side-by-side (more practical maintenance access). Main licensors: UOP\/ Honeywell, Axens\/Stone & Webster, Shell Global Solutions, KBR.<\/p>\n

    Catalyst (ZSM-5 type, Si + Al, 15-50 wt Y-type) is a composite of zeolite, ( Al 20, Si 80, 15 50 Wieht%) alumina matrix, silica binder and kaolin filler.<\/p>\n<\/div>\n

    <\/p>\n

    How a Cat Cracker Works: The Fluid Catalytic Cracking Process and Key Operating Variables<\/h2>\n

    \"How<\/p>\n

    How Does the Catalytic Cracking Process Work Step by Step?<\/h3>\n
      \n
    1. Preheat: vacuum gas oil feed heated to 315-430C through the FCC preheat train heat exchangers before entering the riser bottom. Feed temperature is an important function of the process: lower preheat increases the catalyst : oil ratio and conversion, but may cause feed injector plugging below ~180C.<\/li>\n
    2. Feed Injection: Hot feed atomized by steam through feed nozzles at the riser base, with the reactant vapor immediately contacting hot regenerated catalyst (650-720C). The temp differential vaporizes the feed hydrocarbon in 1ms.<\/li>\n
    3. Cracking in the Riser: Vaporized hydrocarbon and catalyst flow 15-30m up the riser where cracking reactions convert large hydrocarbon molecules into gasoline-range hydrocarbons, LPG olefins and lower fractions within 2-4 s at a riser outlet temperature (ROT) of 510-552C.<\/li>\n
    4. Separation: Reactor cyclones at the riser top separate cracked product vapors from spent catalyst while steam stripping lower cyclones recover additional hydrocarbons from the catalyst before regeneration.<\/li>\n
    5. Regeneration: Catalyst loaded with 0.8-1.2 wt% coke flows through the standpipe to the regenerator where preheated air burns off remaining coke at 700-760C. The exothermic combustion replenishes catalyst activity and heats the catalyst for the next cracking run- the FCC energy engine.<\/li>\n
    6. Fractionation: Cracked vapors enter the main fractionator and are separated by distillation into FCC naphtha, LCO, HCO and slurry oil. Light gases head to downstream gas plant for LPG and dry gas recovery.<\/li>\n
    7. Catalyst return: Hot regenerated catalyst flows back to the riser bottom through the standpipe completing the continuous loop that processes feed 24-7-365 without batch delays.<\/li>\n<\/ol>\n

      Five key operating variables operators adjust to improve FCC performance:<\/p>\n\n\n\n\n\n\n\n\n\n
      Variable<\/th>\nTypical Range<\/th>\nEffect on Yield<\/th>\n<\/tr>\n<\/thead>\n
      Riser Outlet Temp (ROT)<\/td>\n510\u2013552\u00b0C<\/td>\n\u2191 ROT \u2192 \u2191 octane, \u2191 dry gas; gasoline-mode ceiling ~550\u00b0C<\/td>\n<\/tr>\n
      Catalyst-to-oil ratio (C\/O)<\/td>\n4:1 to 8:1 wt\/wt<\/td>\n\u2191 C\/O \u2192 \u2191 conversion, \u2191 coke yield<\/td>\n<\/tr>\n
      Feed preheat temperature<\/td>\n315\u2013430\u00b0C<\/td>\n\u2193 preheat \u2192 \u2191 C\/O; below ~180\u00b0C risks injector fouling<\/td>\n<\/tr>\n
      Overall conversion<\/td>\n65\u201382 wt%<\/td>\nAbove ~82%, over-cracking converts gasoline to dry gas + LPG<\/td>\n<\/tr>\n
      Catalyst activity (MAT)<\/td>\nManaged via fresh catalyst additions<\/td>\n\u2191 activity \u2192 same conversion at lower ROT, less dry gas<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
      \n

      Operator Pro Tip: Wet gas compressor(WGC) capacity is the primary hard throughput constraint. When the WGC limit is hit, back off ROT before feeding down- ROT backoff reduces dry gas and LPG production, freeing compressor while upscaling throughput. Bumping feed preheat delivers similar conversion increases with less dry gas penalty.<\/p>\n<\/div>\n

      <\/p>\n

      Cat Cracker Feedstock and Products: Petroleum Refining Yields Explained<\/h2>\n

      \"Cat<\/p>\n

      Principal feedstock: Vacuum gas oil (VGO) – the 340-550C cut from the vacuum tower produced 200-600+ molecular weight. Heavy for use as transportation fuel, FCC converts it to lighter cuts valued at a premium. Some refiners process atmospheric residue or heavy coker gas oil in dedicated Residue FCC (RFCC) configurations.<\/p>\n

      Feed quality dominates yield profile. A high-saturate VGO (73%+ saturates) can yield more than 60 wt% gasoline; heavy resid or coker gas oil can reduce gasoline yield to 28-38 wt% as coke rises to 6-14 wt%- significant effects on heat balance and regenerator operation.<\/p>\n

      Products of Catalytic Cracking: Full Yield Breakdown<\/h3>\n

      Typical product slate \u2014 commercial VGO FCC unit (riser 521\u00b0C, C\/O 9.3):<\/p>\n\n\n\n\n\n\n\n\n\n\n
      Product<\/th>\nTypical Yield (wt%)<\/th>\nPrimary End Use<\/th>\n<\/tr>\n<\/thead>\n
      FCC Naphtha (gasoline blendstock)<\/td>\n49\u201353 wt%<\/strong><\/td>\nGasoline pool (RON 89\u201394)<\/td>\n<\/tr>\n
      Light Cycle Oil (LCO)<\/td>\n14\u201315 wt%<\/td>\nDiesel blendstock, heating oil<\/td>\n<\/tr>\n
      LPG (C3 + C4 combined)<\/td>\n19\u201323 wt%<\/td>\nAlkylation feed, petrochemicals, LPG fuel<\/td>\n<\/tr>\n
      Dry gas (C1\u2013C2)<\/td>\n2\u20133 wt%<\/td>\nRefinery fuel gas<\/td>\n<\/tr>\n
      Coke<\/td>\n5\u20136 wt%<\/td>\nBurned in regenerator (primary heat source)<\/td>\n<\/tr>\n
      Heavy Cycle Oil \/ Slurry Oil<\/td>\n4\u20135 wt%<\/td>\nFuel oil blending, carbon black feedstock, recycle<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

      Sources: MDPI Processes 2025 (commercial VGO riser data); Sadeghbeigi, R. Fluid Catalytic Cracking Handbook, 2 nd ed. (2000).<\/p>\n

      LPG fraction importance is growing rapidly. FCC accounts for 28% of global propylene. Using ZSM-5 additive, refiners can boost propylene yield by as much as 9%- more value flows into higher-margin petrochemical spec. LPG markets.<\/p>\n

      <\/p>\n

      Cat Cracker Maintenance: Heat Exchangers, Turnaround Planning, and OSHA Compliance<\/h2>\n

      \"Cat<\/p>\n

      How Often Do FCC Units Require Turnaround?<\/h3>\n

      According to AFPP data on 162 FCC turnarounds from 2008-2010 the catalytic cracking industry average is a cycle time of 4 to 5 years – not the 18 to 36 months sometimes cited in older papers. Solomon Associates confirms the median is 4.5 years and current units range from 2 up to 9 years. KBR has explicitly said, “A normal FCC turnaround cycle is about five years.” A BP report of a number of units describes turnaround intervals of 5 to 6 years with good onstream management.<\/p>\n

      FCC units running heavy residues feeds (conradson carbon greater than 3 wt%) can only expect intervals of 2 to 3.5 years.<\/p>\n

      <\/p>\n

      \n

      Counter-Intuitive FCC Bottleneck: Industry discussion generally revolves around catalyst activity as the dominant FCC performance variable – and catalyst management is well demonstrated via continuous equilibrium catalyst (e-cat) monitoring. What AFPP\u2019s 162-unit survey and BP\u2019s plant operational data indicate, though, is that precipitous reboiler and other heat exchanger fouling in the preheat train is where units are truly limited when trying to run beyond four-five years. Catalyst deactivation is known and felt on the bottom line through ongoing catalyst management; un-anticipated heat exchanger fouling is not – and thus third-party preventive HX maintenance is arguably the single highest increase-income measure to maximize FCC production.<\/p>\n<\/div>\n

      Primary FCC turnaround inspection scope (in priority order):<\/strong><\/p>\n