Oil-to-Chemicals Configurations Comprehensive Notes

Oil-to-Chemicals Configurations

Introduction

  • Whole crude oil is typically fractionated into naphtha, diesel, kerosene, gas oil, and residuum.
  • Some fractions serve as feedstock for olefin production in the petrochemical industry.
  • Conventional olefin production involves substantial, expensive, and energy-demanding refining processes.
  • Crude-to-chemicals aims to directly crack crude oil into chemicals like ethylene, propylene, and light aromatics.
  • This direct cracking should be economically viable without conventional refining steps.
  • Direct conversion of crude oil to chemicals provides an additional advantaged feedstock route to chemicals and helps bridge future petrochemical feedstock gap.
  • It also helps create new demand for crude oil, should use of transportation fuels from crude oil stagnate or decline.
  • Direct conversion of crude oil to chemicals helps close the widening supply-demand gap for key building blocks normally produced as co-products (propylene, butadiene) due to the increasing shift toward cracking lighter feedstock spurred by the shale gas revolution.

Crude to Chemicals Concept

  • Crude-to-Chemicals (C2C) is a technology that directly converts crude oil into high-value chemical products instead of transportation fuels.
  • C2C enables chemical production with yields exceeding 70%-80% of the barrel, compared to ~10% in a non-integrated refinery.
  • In C2C, refinery and petrochemical plants are merged into one plant.

Drivers for Crude-to-Chemicals

  • The conventional route to petrochemicals starts with distillates, usually naphtha.
  • C2C takes advantage of the cost of crude oil as a direct feed versus naphtha.
  • C2C uses a cost-effective route to directly convert crude oil into chemicals.
  • Cost savings are significant, avoiding costs associated with separating and purifying distillates.
  • Refiners face declining demand for gasoline and fuel production due to carbon emission mandates, greater vehicle fuel efficiency, and increasing electric vehicle demand.
  • This shift is predicted to reduce fuel-based demand growth for crude oil.
  • Oil refiners see an opportunity to convert low-value oil into high-value chemicals.
  • C2C elevates petrochemical production to the refinery scale, a roughly 4X increase from current world-scale petrochemical plants.
  • C2C can double the profitability from a barrel of crude oil for global refiners.
  • C2C creates new demand for oil and ensures sustainable business growth with advantaged feedstock.
  • It helps divert oil from fuel to chemical production, reducing combustion and enabling CO2 capture in chemicals to meet environmental regulations.
  • C2C meets new stringent IMO-2020 regulations for fuel oils (ULSFO).
  • Integrated refineries are designed with bottom-of-the-barrel upgrading.

Crude-to-Chemicals Complex vs. Traditional Refinery

  • Crude oil refineries are generally oriented to transportation fuels, with some production of building blocks for the petrochemical industry (light olefins and BTX).
  • Traditional refineries need to change to remain profitable by:
    • Maximizing feedstock conversion into light chemicals and minimizing fuel products.
    • Ensuring feed and product flexibility to adjust to changing market drivers.
    • Optimizing energy use (fuel and power) to meet demands for high severity, high conversion processes.
    • Meeting stricter emissions laws.
    • Optimizing configuration to meet CAPEX and OPEX goals.
  • Even in integrated schemes, refineries still aim to produce fuels, while petrochemical complexes focus on chemical production.
  • In a C2C complex, the two plants merge into one, primarily producing chemicals.
  • Refinery products include fuels, lube base oil, and energy, allowing for crude and feed flexibility (ethane, LPG, condensate splits).
  • Petrochemicals include C4, reformate, and propylene, aiming to minimize fuels and maximize chemicals.
  • Global refinery product yields show chemicals at 8%, compared to Petro Rabigh and Hengli Refinery with higher percentages.
  • Conventional refineries use CCR and FCC processes as main sources for chemicals.
  • A typical refinery configuration involves various units like CDU/VDU, Diesel HDT, VGO HDT, Kerosene HDT, ALK, Naphtha HDT, FCC, and CCR to produce gasoline, toluene, benzene, diesel, propylene, kerosene, and xylenes.
  • Reformer yields include hydrogen-rich gas (7-10 wt.%, with 1.5-3% pure hydrogen), fuel gas (1-3 wt.%), propane (3-5 wt.%), butane (5-8 wt.%, about 50% isobutane), and reformate (65-85 wt.%, aromatics content > 50%).
  • FCC yields vary based on feed (Hydrotreated VGO feed).
  • PetroRabigh complex configuration includes CDU/VDU, Diesel HDT, VGO HDT, Kerosene HDT, ALK, Naphtha HDT, HO-FCC, and an Aromatics Complex to produce gasoline, PX, benzene, diesel, propylene, ethylene, and other products.
  • Steam cracker yields vary.
  • Aromatics plants have a simplified block flow diagram for aromatic production.
  • Hengli Refinery - PX Complex Configuration involves conversion of distillates and bottom to naphtha and an aromatic complex for PX and benzene.
  • Hengli's PX complex configuration processes 400,000 bpsd of crude oil, including Saudi Heavy, Saudi Medium, and Marlim, with an average API of 27.62 and sulfur content of 2.26%.

Crude-to-Chemicals Configurations

  • Direct crude oil processing in steam crackers was unsuccessful due to heavy hydrocarbons causing rapid coke formation.
  • A key C2C strategy involves conditioning feedstock oil (rejecting heavy fraction and contaminants) and upgrading the rest before feeding it to the steam cracker.
  • The rejected part can be used as fuel or upgraded separately.
  • After conditioning/upgrading, two main C2C approaches are considered: steam cracking centered and fluid catalytic cracking centered processes, both combinable with an aromatics complex.
  • Further boost achieved by integrating additional conversion units downstream of the Steam Cracker / Catalytic Cracker.
  • C2C Strategy to Maximize Chemicals Production includes crude oil rejection of heavy fraction, steam cracking/catalytic cracking, aromatics complex, primary conversion, secondary conversion (OCM, metathesis, MTBE), hydrotreating, and bottom-of-the-barrel conversion/hydrocracking.
  • Three emerging strategies are predominantly used in C2C:
    • Direct processing of crude oil in steam cracking (ExxonMobil, Shell).
    • Integrated hydro-processing/de-asphalting and steam cracking.
    • Processing of middle distillates and residues using hydrocracking technology.
  • Crude conditioning/upgrading is crucial, especially for heavier aromatics and polynuclear aromatics which should never be fed to cracking heaters.
  • Corma et. Al. , Catal. Sci. Technol., 2017, 7, 12-46, details crude conditioning/upgrading.
  • Crude-to-Chemicals requires increasing the conversion of gas oils and residue to light liquids by adding process units.
  • Feed conditioning enhances paraffin content, upgrades vacuum residue, and reduces contaminants like sulfur and metals.
  • Technology alternatives exist for each step, with distillate hydrocracking and residue conversion being important.
  • Hydrocracker is important in feed conditioning, maximizing heavy naphtha for catalytic reforming or converting VGO and Diesel to naphtha for a steam cracker.
  • Vacuum residue (30-40% of complex feed for heavy crudes) requires additional processing to convert to lighter, hydrogen-rich hydrocarbons.
  • Heavier oil has a higher amount of heavy residue.
  • As density increases, the H:C ratio decreases, and sulfur and metal impurities (Ni +V) increase. Any process to produce more chemicals from crude oil requires to:
    1. Reduce heavy residue to lower molecules
    2. Raise H:C ratio around 2 for all chemicals
    3. Reduce sulfur and metal impurities
  • Residue conversion consumes significant energy and increases complex investment.
  • Some residue conversion processes produce waste material (spent catalyst, waste pitch, high-sulfur petroleum coke).
  • Residue conversion technology selection maximizes the economic of C2C complexes and ensures compliance with environmental standards.
  • Crude conditioning/upgrading methods include hydrotreating, hydrocracking, hydrovisbreaking, visbreaking, solvent deasphalting, catalytic cracking, and coking.
  • One critical configuration decision is how to process fractions heavier than middle distillates.
  • Different feed conditioning approaches can be pursued to improve “Oil-to-Chemicals” strategy and complex margins.
  • Parameters to manage when selecting vacuum residue conversion technology include:
    • Investment cost
    • Feed flexibility
    • Energy management
    • Hydrogen consumption
    • Cost and disposition of unconverted pitch and tar
    • Cost of fresh catalysts and disposition of spent catalysts
    • Environmental impacts of the overall complex

Historical Overview of Crude Oil to Chemicals Processes

  • Industry-wide research into direct crude oil to chemicals conversion has been ongoing since the 80s.
  • Equistar Chemicals process (USP7019187) involves preheating the feedstock and subjecting it to mild catalytic cracking conditions until substantially vaporized, followed by steam cracking the lighter vaporized fraction under severe conditions (790-840 ºC). Steam is introduced at the bottom of the vaporizer at temperatures up to 700ºC, with packing used to enhance steam/liquid contact. Hydrogen can also be fed to the system to reduce coking. Claims of 97 wt% vaporization of a Sahara blend crude assisted with steam at 704ºC were reported.
  • Shell process (US6,632,351) involves pre-heating the crude oil in two stages to 375-415 oC with inter-stage vapor-liquid separators. A specially designed vapor/liquid separator creates a swirl at the upper inlet to remove the non-vaporized part from the gas stream. The preheated gas is sent to the radiant zone, and the centrifuge effect forces liquid droplets downwards in a thin film, allowing the gas stream to be hotter than in a conventional flash drum and minimizing coking. A. Corma et. Al. , Catal. Sci. Technol., 2017, 7, 12-46, provides details.
  • Aramco/SABIC COTC Complex is a combined refinery and chemicals complex to produce maximum chemicals and feeds to a steam cracker. Crude oil is fractionated into traditional cuts and fed to dedicated steam cracker furnaces after treatment. The traditional refinery is converted to produce a much higher proportion of steam cracker friendly feedstocks (LPG and naphtha). Chemical conversion is about 40-60% per barrel of oil.
  • Many companies pursued direct cracking of crude oil using various approaches during 1950-1980s with demonstration plants, but faced fluctuating crude oil prices, high coking problems, frequent shutdowns, operational issues from heavy residues, poor economics, operational challenges and complex reactor design
  • Processes to overcome coking used fluidized bed or thermal cracking.
  • Main Historical Processes:
    • BASF: Fluid bed, feed partial combustion, coke particles, 725°C, 41.5% C2-C4 olefins yield.
    • UBE: Fluid bed, feed partial combustion, inorganic oxide particles, 840°C, 47.8% C2-C4 olefins yield.
    • Lurgi: Fluid bed, coke burning, sand particles, 760°C, 41.6% C2-C4 olefins yield.
    • Kunugi/Kunii: Fluid bed, coke burning, coke particles, 750°C, 34% C2-C4 olefins yield.
    • Dow: Thermal, feed partial combustion, no particles, 1200°C, 39.0% C2-C4 olefins yield.
    • Mitsui: Thermal, feed partial combustion, molten salts particles, 750°C, 41.5% C2-C4 olefins yield.
    • Chiyoda (ACR): Thermal, superheated steam, no particles, 850°C, 52.0% C2-C4 olefins yield.
  • Kunugi and Kunii (KK) process (MITI Japan) uses a fluidized bed reactor with coke as a heat carrier, with excessive heat coke regenerated. Yields are Ethylene: 12-24 wt%, Propylene: 6 -10 wt%.
  • UBE Process uses partial combustion with oxygen in a fluidized bed using inorganic oxide particles as a heat carrier, with Ethylene yield 28 wt%, Propylene yield 11 wt%, C4s yield 8 wt%.
  • Lurgi- Sand Cracker Process uses fine grained sand that has been heated in a conveyor tube by a fuel oil flame, Ethylene yield 20-23 wt%, Propylene yield 12-13 wt%, Butadiene yield 3-4 wt%.
  • BASF- Fluidized Coke Cracking Process uses partial combustion in the reactor to provide heat, with Coke particles, Ethylene yield 20-23 wt%, Propylene yield 11-12 wt%, C4=s yield 4-5 wt%.
  • Advanced Cracking Reactor (ACR) Process (Union Carbide/Kureha/Chiyoda) uses superheated steam produced by partial combustion as the heat carrier, Ethylene yield 32 wt%, Propylene yield 12 wt%, C4s yield 8 wt%.
  • Dow partial combustion oil cracking process (PCC) uses superheated steam produced by partial combustion as the heat carrier. The reactor consists of partial combustion, shift reaction, and cracking zones at temperatures of about 1910oC, 905oC, and 1210oC, respectively. The residence time is about 0.15s. The O2-to-fuel and steam-to-fuel ratios are both around 1.8. The O2-to-feed and total steam-to-feed ratios are 0.8 and 3.3, respectively.
  • Mitsui – COSMOS Process uses molten salt as both the heat carrier and catalyst to prevent coke formation, using an external heated tubular furnace, Ethylene yield 25-26 wt%, Propylene yield 11-12 wt%, C4s yield 6-7 wt%.

New Novel Technologies for Crude to Chemicals

  • Major competitors file/grant patents in crude to chemicals through catalytic processes.
  • Conventional steam cracking systems are effective for high-quality feedstocks with light volatile hydrocarbons (gas oil and naphtha).
  • Steam cracking economics sometimes favor lower-cost feedstocks (heavy gasoil, atmospheric residue).
  • These feedstocks contain high-molecular-weight, nonvolatile components (boiling points > 590°C), which form coke in conventional pyrolysis furnaces.
  • Cracking heavier feeds produces large amounts of tar, leading to coking and rapid fouling in TLEs.
ExxonMobil Technology (US7,588,737)
  • The process involves crude oil pre-heating in the convection section.
  • Dilution steam is added, and the mixture is heated to 315-550 oC.
  • The pre-heated feed is routed to a flash drum.
  • Vapors from the flash drum are sent to the radiant section of the furnace.
  • Superheated steam is introduced at the bottom of the flash drum to maximize recovery of lighter material and route it to the steam cracking furnace.
  • Residue from the bottoms of the flash drum can be recycled.
  • Launched as the world’s first C2C in Singapore in 2014 (1MT/year ethylene plant) with a reported maximum 50% yield to chemicals.
  • The technology uses a specially modified cracking furnace with an external flash pot for separating light, crackable crude oil components from heavier components.
  • External vaporization drum is used for crude oil feed; A first flash removes a naphtha cut as vapor, A second flash removes vapor of boiling point 230–590°C.
  • The vaporization drum tangentially introduces the hydrocarbon mixture into the flash vessel, forming an annular flow along the inside flash drum wall. Volatile vapor phase initially forms an inner core and flows upward; hot liquid hydrocarbon falls to the bottom effortlessly (centrifugal effect).
  • The use of an internal condenser maximizes hydrocarbon recovery 7. New Novel Technologies for Crude to Chemicals as crackable material while using increased flash drum temperature and prevents carryover of heavy hydrocarbons
  • There is a small difference between crude oil and naphtha processes in terms of design sizes for major equipment
Saudi Aramco TC2C™ Technology
  • It is the most mature technology in Saudi Aramco’s Crude to Chemicals research program.
  • The TC2C™ Technology involves a pretreatment step of crude oil (conditioning) which feeds directly into a steam cracker to produce ethylene and propylene as major products.
  • The conditioned feed has less polyaromatics and more paraffins.
  • A key technology component of the fixed-bed hydro processing is Saudi Aramco’s novel hydrocracking catalyst containing tailored mesoporous zeolite. It exhibit an expected long run length (low start‐of‐run temperature) and a commensurately high yield of lighter products without excessive methane production.
  • The feed conditioning section includes fixed-bed and liquid circulation reactors, smartly configured to selectively condition crude oil for steam cracking into petrochemicals.
  • Another key innovative concept of TC2C™ is the Vapor Liquid Separation Device (VLSD) developed at Saudi Aramco R&D Center with an objective to reject heavies in the crude. It was successfully integrated with Lummus’s Heavy Oil Processing System (HOPS) technology.
  • Novel integrations with steam crackers to maximize high-value chemicals.
  • The first commercial deployment of TC2C™ technology is underway (ERC 2024).
  • Chemicals yield of >70 wt.% from AL and AXL crudes is reported.
  • Example of operating conditions and properties for the crude conditioning step include:
    • Reactor Pressure – 150 bar
    • SOR Temperature - 370oC
    • Deactivation Rate - 1.45oC/mo
    • Chemical H2 Cons. – 0.6 wt%.
Saudi Aramco CC2C™ Technology
  • CC2C™ technology involves direct cracking of crude oil in a high severity dual-down-flow reactor system after first flashing the crude oil into light and heavy boiling fractions.
  • The two reactors share a common regenerator unit and a single catalyst.
  • It leverages the high severity fluid catalytic cracking (HS-FCC) technology platform, developed by Saudi Aramco and partners.
Reliance MCC Technology
  • MCC is a new process developed for direct cracking of crude along with other distress streams.
  • Cracking takes place sequentially in multi-zone cracking in a single riser.
  • The riser is divided into three temperature zones in which different hydrocarbon feeds are introduced.
  • Severity in each zone drops gradually in different sections of the riser from bottom to top to suit different crackability needs of different feed/fraction.
  • Multi-zone severity of riser also allows processing non-conventional feedstock like full crude oils, condensate, olefinic naphtha (not processable in Steam cracker).
  • Methanol feed is introduced at the top zone of the riser to synergize endothermic cracking of hydrocarbons with exothermic cracking of oxygenates for a good heat balance and enhance light olefins yield.
  • This integrates Steam Cracking (SC), high severity Fluid Catalytic Cracking (FCC) and Methanol to Olefins (MTO).
  • Yields of Propylene (> 30wt %) and Ethylene (>18wt %) and BTX (15%) are reported.
  • The riser has different zones with varying temperatures, WHSV, and severity to process different feeds.
  • MCC can be integrated in refinery setup
Hengli's PX complex configuration
  • Hengli's PX complex configuration processes 400,000 bpsd of crude oil, including Saudi Heavy, Saudi Medium, and Marlim, with an average API of 27.62 and sulfur content of 2.26%. The configuration involves several units for light hydrocarbon recovery, kerosene hydrotreating, naphtha hydrogenation, heavy naphtha processing, continuous reforming, atmospheric and vacuum distillation, diesel hydrocracking, resid ebullated bed hydrocracking, gasoil hydrocracking, solvent de-asphalting, residue gasification, and production of PX, benzene, and lube oil.