Recommended Process Routes for Maximized Oil Conversion to Aromatics and Olefins

The refining industry has evolved over time in order to adapt to the market trends. In order to maximize chemicals yield, they have no choice but to increase the conversion yield. This can be achieved by building the right configuration involving advanced integrated complex schemes.

The ultimate integration degree results in the grassroots Crude-to-Chemicals (CTC) complexes. Although plants showing various integration levels co-exist today, market trends clearly show that the higher the integration level, the higher the flexibility and the capability essential to match the evolving market requiring more petrochemicals, with a lower appetite for fuels.

A CTC complex is structured around three main blocks: Conversion, Olefins and Aromatics.

The very first block is the conversion of the crude with the specific goals of maximizing the transformation of heavier streams into light and heavy naphthas. As the conversion is to be pushed to increase the naphtha yield, this block will determine the economic returns of the olefins block and the aromatics block – respectively designed to process the light naphtha, for the olefins production; and the heavy naphtha, for the aromatics production.

The Production Target, the Key to Unlock the Full Potential of the Conversion Block

Innovative integration strategies between the refinery and downstream petrochemical assets begins with the Bottom-Of-the-Barrel (BOB) upgrading, to supply the naphtha feedstock for petrochemicals production or even directly olefinic monomers and aromatics-rich raw cut.

Depending on whether the key target is olefins or aromatics production, the
conversion block would involve a different combination of technologies for an optimum yield:

• Resid Conversion to Olefins: targeting olefins, fluid catalytic cracking (FCC) is the preferred unit to convert residue fractions to light components, olefins as well as gasoline. Direct propylene production from FCC technologies covers a third of the total worldwide propylene production. Downstream purification is crucial for reaching olefinic product quality. Aromatics content in the co-produced naphtha is higher, thus becoming a more valuable stream to be sent to the aromatics block.
• Resid Conversion to Naphtha: ebullated-bed based process technology in association with maxi naphtha fixed-bed hydrocrackers, are involved in this strategy and succeed in reaching the naphtha production even processing the most refractory feeds.

The conversion block consisting of the BOB upgrading, would be either centered on two different families of technologies embedded in the right configuration for the overall scheme:

• Hydrogen Addition route: the conversion of the Vacuum Residue (VR) or Atmospheric Residue (AR) by the means of Residue Hydrocracking, consists of the Hydrogen Addition route. The conversion is obtained through the hydrogenation of the residues and cracking reaction under high hydrogen partial pressure. The effluent has a higher hydrogen content than the feed to the unit.
• Carbon Rejection route: this route refers to the conversion of the VR or AR using high temperature resulting to direct olefins and raw aromatics production. Delayed Coker unit produces coke as by-product, unlike the Fluidized Catalytic Cracking unit where the internal combustion of the coke provides the heat required and the FLEXICOKING™ where the coke gives rise to syngas.

Olefins Block, Targeting the Highly Coveted Olefins

The olefins block includes the purification of the olefinic cuts, oligomerization processes and selective cracking into propylene. The optimization of the steam-cracker feed is also part of the equation.

FCC and Steam-Cracker (SC) are the two common routes to generate olefins. Whereas the new breakthrough high severity FCC technology, HS-FCC™, has been developed to overcome the barriers to boosting olefins production, steam-cracking consists of the most widespread process for the production for the production of light olefins, mainly ethylene, propylene and butadiene.

Aromatics Block, Towards Specialty Chemicals

The aromatics block encompasses all the technologies from aromatization reactions up to aromatics solvent extraction, aromatics skeleton rearrangement and pure xylene isomers production to get in particular the highly coveted paraxylene molecule.

When targeting Aromatics production, the CTC conversion block maximizes Heavy Naphtha (HN) production for the aromatics block of a petrochemical complex.

The main entry point to the aromatics block is typically a reforming technology dedicated to the production of aromatics from heavy naphtha. It is the first step to high-purity paraxylene (PX), key intermediate in the value chain in the manufacture of the polyethylene terephthalate (PET) and fiber-consuming products. 

The aromatics block incorporates a tailor-made arrangement of four blocks, constituting the ParamaX® technology suite, dedicated to selective production of a wide range of aromatics that also include metaxylene, orthoxylene, benzene and toluene:

• Aromatics Production
• Aromatics Extraction
• Aromatics Rearrangement
• Pure Xylene Isomers Production

CTC Project Viability and Implementation

Multi-criteria analysis includes cost estimation and financial analysis to ascertain the construction project’s overall viability and is complemented with audits regarding energy, water footprint and CO₂ emissions that acts as a decision-making support. Therefore investors shift from “I want to invest in petrochemicals” towards “here is my project, and this is the path”. The selection of the best combination arises from the holistic view essential to perform scheme optimization through the combination of technologies suites and to support the customer to the best scheme selection.

Knowledge of crude oils is also essential for guiding the client on crude selection and on proper blending and to select the most appropriate processes as a function of the feed quality. The mastery of the whole chain of the unit life cycle is a must to ensure maximum synergy & asset optimization connecting the various blocks.