FCC to Olefins as Strategy to Overcome the Challenges Imposed by the Hostile Scenario for Fossil Fuels

Introduction and Context

The current scenario present great challenges to the crude oil refining industry, prices volatility of raw material, pressure from society to reduce environmental impacts and refining margins increasingly lower. The newest threat to refiners is the reduction of the consumer market, in the last years became common, news about countries that intend to reduce or ban the production of vehicles powered by fossil fuels in the middle term, mainly in the European market. Despite the recent forecasts, the transportation fuels demand is still the main revenues driver to the downstream industry, as presented in Figure 1, based on data from Wood Mackenzie Company.

Figure 1 – Global Oil Demand by Derivative (Wood Mackenzie, 2020)

According to Figure 1, is expected a growing demand by petrochemicals while the transportation fuels tend to present falling consumption. Still according to Wood Mackenzie data, presented in Figure 2, due to the higher added value, the most integrated refiners tend to achieve higher refining margins than the conventional refiners which keep the operations focused on transportation fuels.

Figure 2 – Refining Margins to Integrated and Non-Integrated Refining Hardware (Wood Mackenzie, 2020)

NCM = Net Cash Margins

The improvement in fuel efficiency, growing market of electric vehicles tends to decline the participation of transportation fuels in the global crude oil demand. New technologies like additive manufacturing (3D printing) have the potential to produce great impact to the transportation demands, leading to even more impact over the transportation fuels demand. Furthermore, the higher availability of lighter crude oils favors the oversupply of lighter derivatives that facilitate the production of petrochemicals against transportation fuels as well as the higher added value of petrochemicals in comparison with fuels.

Figure 3 present an overview of the trend of growing to the petrochemical market in middle term.

Figure 3 – Growing Trend in the Demand by Petrochemical Intermediates (Wood Mackenzie, 2020)

As aforementioned, face the current trend of reduction in transportation fuels demand at the global level, the capacity of maximum adding value to crude oil can be a competitive differential to refiners. Due to the high capital investment needed for the implementation that allows the conventional refinery to achieve the maximization of chemicals, capital efficiency becomes also an extremely important factor in the current competitive scenario as well as the operational flexibility related to the processed crude oil slate.

Considering exclusively the propylene market, the forecasts are even more encouraging for investments in on purpose propylene production routes. Figure 4 presents the projection to propylene market size for the next years.

Figure 4 – Evolution of Propylene Market Size for the next years (Precedence Research, 2022)

According to Figure 4, the propylene market size can reach values higher than 162 billion USA dollars in 2034 with an annual rate of 3,76 % with Asia being the bigger market as expected.

Facing these challenges, search for alternatives that ensure survival and sustainability of the refining industry became constant by refiners and technology developers. Due to his similarities, better integration between refining and petrochemical production processes appears as an attractive alternative. Although the advantages, it’s important consider that the integration between refining and petrochemical assets increase the complexity, requires capital spending, and affect the interdependency of refineries and petrochemical plants, these facts need to be deeply studied and analyzed case by case. In this business environment, flexible refining technologies like Fluid Catalytic Cracking (FCC) can ensure high competitiveness to refiners once are capable to produce high quality intermediates both to petrochemicals and transportation fuels, in markets with great demand by petrochemicals, the petrochemical FCC technologies can be an attractive option, despite the high capital spending. Refiners with restriction of capital investment can even maximize the profitability of FCC units through optimization actions aiming to maximize the yield of petrochemicals against transportation fuels.

Synergies between Refining and Petrochemical Assets – Petrochemical Integration

The focus of the closer integration between refining and petrochemical industries is to promote and seize the synergies existing opportunities between both downstream sectors to generate value to the whole crude oil production chain. Table 1 presents the main characteristics of the refining and petrochemical industry and the synergies potential.

As aforementioned, the petrochemical industry has been growing at considerably higher rates when compared with the transportation fuels market in the last years, additionally, represent a noblest destiny and less environmental aggressive to crude oil derivatives. The technological bases of the refining and petrochemical industries are similar which lead to possibilities of synergies capable to reduce operational costs and add value to derivatives produced in the refineries.

Figure 5 presents a block diagram that shows some integration possibilities between refining processes and the petrochemical industry.

Figure 5 – Synergies between Refining and Petrochemical Processes

Process streams considered with low added value to refiners like fuel gas (C2) are attractive raw materials to the petrochemical industry, as well as streams considered residual to petrochemical industries (butanes, pyrolysis gasoline, and heavy aromatics) can be applied to refiners to produce high quality transportation fuels, this can help the refining industry meet the environmental and quality regulations to derivatives.

The integration potential and the synergy among the processes rely on the refining scheme adopted by the refinery and the consumer market, process units as Fluid Catalytic Cracking (FCC) and Catalytic Reforming can be optimized to produce petrochemical intermediates to the detriment of streams that will be incorporated to fuels pool. In the case of FCC, installation of units dedicated to produce petrochemical intermediates, called petrochemical FCC, aims to reduce to the minimum the generation of streams to produce transportation fuels, however, the capital investment is high once the severity of the process requires the use of material with noblest metallurgical characteristics.

The IHS Markit Company proposed a classification of the petrochemical integration grades, as presented in Figure 6.

Figure 6 – Petrochemical Integration Levels (IHS Markit, 2018)

According to the classification proposed, the crude to chemicals refineries is considered the maximum level of petrochemical integration. It’s important to quote that the crude to chemicals technologies have a deep dependence of the high severity FCC technologies, normally a petrochemical FCC unit is applied.

Fluid Catalytic Cracking Technologies – An Overview

Fluid Catalytic Cracking (FCC) is one of the main processes which give higher operational flexibility and profitability to refiners. The catalytic cracking process was widely studied over last decades and became the principal and most employed process dedicated to converting heavy oil fractions in higher economic value streams.

The installation of catalytic cracking units allows the refiners to process heavier crude oils and consequently cheaper, raising the refining margin, mainly in higher crude oil prices scenario or in geopolitics crises that can become difficult the access to light oils.  The typical Catalytic Cracking Unit feed stream is gas oils from vacuum distillation process. However, some variations are found in some refineries, like sending heavy coke naphtha, coke gas oils and deasphalted oils from deasphalting units to processing in the FCC unit.

The catalyst normally employed in fluid catalytic cracking units is a solid constituted by small particles of alumina (Al2O3) and silica (SiO2) (zeolite). By the catalyst characteristics and the operational conditions in the catalytic cracking process (temperature higher than 500 oC), the process is inefficient to cracking aromatic compounds, therefore, how much more paraffinic is the feedstream, higher is the unit conversion. Figure 7 presents a process scheme for a typical Fluid Catalytic Cracking Unit (FCCU).

In a conventional scheme, the catalyst regeneration process consists in the carbon partial burning deposited over the catalyst, according to chemical reaction below:

C + ½ O2 → CO

The carbon monoxide is burned in a boiler capable of generating high pressure steam that supplies others process units in the refinery.

Figure 7 – Schematic Process Flow for a Typical Fluid Catalytic Cracking Process Unit (FCCU)

The principal operational variables in a fluid catalytic cracking unit are reaction temperature, normally considered the temperature in the top of the reactor (called riser), feed stream temperature, feed stream quality (mainly carbon residue), feed stream flow rate and catalyst quality. Feedstock quality is especially relevant, but this variable is a function of the crude oil processed by the refinery, so is difficultly can be changed, but for example, aromatic feedstock’s with high metals content are refractory to cracking and conducting to a quick catalyst deactivation.

An important variation of the fluid catalytic cracking technology is the residue fluid catalytic cracking unit (RFCC). In this case, the feedstock to the process is basically residue from atmospheric distillation column, due to the high carbon residue and contaminants (metals, sulphur, nitrogen, etc.) are necessary some adaptations in the unit like catalyst with higher resistance to metals and nitrogen and catalyst coolers furthermore, it’s necessary apply materials with most noble metallurgy due the higher temperatures reached in the catalyst regeneration step (due the higher coke quantity deposited on the catalyst), that raises significantly the capital investment to the unit installation. Nitrogen is a strong contaminant to the FCC catalyst because they neutralize the acid sites of the catalyst which are responsible for the cracking reactions.

When the residue has high contaminants content, is common the feed stream treatment in hydrotreating units to reduce the metals and heteroatoms concentration to protect the FCC catalyst.

Typically, the average yield in fluid catalytic cracking units is 55% in volume in cracked naphtha and 30 % in LPG.

The decanted oil stream contains the heavier products and have high aromatic content, is common that this product is contaminated with catalyst fines and normally this stream is directed to use like fuel oil diluent, but in some refineries, this stream can be used to produce black carbon.

Light Cycle Oil (LCO) has a distillation range close to diesel and normally this stream is directed to treatment in severe hydrotreating units (due to the high aromaticity), after this treatment the LCO is sent to the refinery diesel pool.

Heavy cracked naphtha is normally directed to refinery gasoline pool, however, in scenarios where the objective is to raise the production of middle distillates, this stream can be sent to hydrotreating units for further diesel production.

The overhead products from main fractionator are still in gaseous phase and are sent to the gas separation section.  The fuel gas is sent to the refinery fuel gas ring, after treatment to remove H2S, where will be burned in fired heaters while the LPG is directed to treatment (MEROX) and further commercialization.   The LPG produced by FCC unit have a high content of light olefins (mainly Propylene) so, in some refineries, the LPG stream is processed in a Propylene separation unit to recovery the propylene that has higher added value than LPG.

Cracked naphtha is usually sent to refinery gasoline pool which is formed by naphtha produced by other process units like straight run naphtha, naphtha from the catalytic reforming unit, etc. Due to the production process (deep conversion of residues), the cracked naphtha has high sulfur content and to attend the currently environmental legislation this stream needs to be processed to reducing the contaminants content, mainly sulfur.

The cracked naphtha sulfur removing represents a great technology challenge because is necessary to remove the sulfur components without molecules saturation that gives high octane number for gasoline (mainly olefins).

Usually, catalytic cracking units are optimized to aiming the production of fuels (mainly gasoline), however, some process units are optimized to maximize the light olefins production (propylene and ethylene). Process units dedicated for this purpose have his project and operational conditions significantly changed once the process severity is strongly raised in this case.

The reaction temperature reaches 600 oC and higher catalyst circulation rate raises the gases production, which requires a scaling up of gas separation section.

In several cases, due the higher heat necessity of the unit is advantageous to operate the regenerator with the total combustion of the coke deposited on the catalyst, this arrangement significantly changes the thermal balance of the refinery once it’s no longer possible to resort the steam produced by the CO boiler.

Over last decades, the fluid catalytic cracking technology was intensively studied aiming mainly the development of units capable of producing light olefins (Deep Catalytic Cracking) and to process heavier feedstocks. The main licensers for fluid catalytic cracking technology nowadays are the companies KBR, UOP, Stone & Webster, Axens, and Lummus Company.

Meeting the Market Demand through FCC Optimization – Maximum Olefins Operation Mode

In this operation mode the FCC unit operates under high severity translated to high operation temperature (TRX), high catalyst/oil ratio. The catalyst formulation considering higher catalyst activity through addition of ZSM-5 zeolite. There is the possibility to a reduction in the total processing capacity due to the limitations in blowers and cold area capacity.

It’s observed an improvement in the octane number of cracked naphtha despite a lower yield, due to the higher aromatics concentration in the cracked naphtha. In some cases, the refiner can use the cracked naphtha recycle to improve even more the LPG yield.

In the maximum LPG operation mode, the main restrictions are the cold area processing capacity, metallurgic limits in the hot section of the unit, treating section processing capacity as well as the top systems of main fractionating column. In markets with falling demand by transportation fuels, this is the most common FCC operation mode.

Through changing the reaction severity, it is possible to maximize the production of petrochemical intermediates, mainly propylene in conventional FCC units, as shown in Figure 8.

Figure 8 - Optimization of Process Variables in FCC Units to Improve the Yield of Petrochemicals Intermediates.

The use of FCC catalyst additives such as ZSM-5 can increase unit propylene production by up to 9,0%. Despite the higher operating costs, the higher revenues from the higher added value of derivatives should lead to a positive financial result for the refiner, according to current market projections. A relatively common strategy also applied to improve the yield of LPG and propylene in FCC units is the recycling of cracked naphtha leading to an over cracking of the gasoline range molecules.

Maximizing Olefins in the Refining Hardware – The Petrochemical FCC Technologies

As quoted earlier, in markets with high demand by petrochemicals, the petrochemical FCC can be an attractive alternative to refiners aiming to ensure higher added value to bottom barrel streams. An example of FCC technology developed to maximize the production of petrochemical intermediates is the PetroFCC™ process by UOP Company, this process combines a petrochemical FCC and separation processes optimized to produce raw materials to the petrochemical process plants, as presented in Figure 9. Other available technologies are the HS-FCC™ process commercialized by Axens Company, and INDMAX™ process licensed by Lummus Company. The basic process flow diagram for HS-FCC™ technology is presented in Figure 10.

Figure 9 – PetroFCC™ Process Technology by UOP Company. Source: Honeywell UOP - www.uop.honeywell.com

It’s important to considering that both technologies presented in Figures 9 and 10 are based on Petrochemical FCC units that presents especial design due to the most severe operating conditions.

Figure 10 – HS-FCC™ Process Technology by Axens Company.

To petrochemical FCC units, the reaction temperature reaches 600 oC and higher catalyst circulation rate raises the gases production, which requires a scaling up of gas separation section.  The higher thermal demand makes advantageous operates the catalyst regenerator in total combustion mode leading to the necessity of installation a catalyst cooler system.

Figure 11 presents the results of a comparative study, carried out by Technip Company, showing the yields obtained by conventional FCC units, optimized to olefins (FCC to olefins), and the HS-FCC™ designed to maximize the production of petrochemical intermediates.

Figure 11 – Comparative Study between Conventional FCCs and Petrochemical FCC (HS-FCC™)

It’s observed a higher reaction temperature (TRX) and a cat/oil ratio five times higher when are compared the conventional process units and the petrochemical FCC (HS-FCC™), leading to a growth of the light olefins yield (Ethylene + Propylene + C4=’s) from 14 % to 40%.

Among another petrochemical FCC technologies, it’s possible to quote the Maxofin™ and K-COT™ processes developed by KBR Company and the SCC™ technology developed by Lummus Company.

Due to the higher production of light olefins, mainly ethylene, another important difference between conventional and petrochemical FCC units is related to the gas recovery section, while in conventional FCC is applied absorber columns, in petrochemical units is applied cryogenic processes though refrigeration cycles in similar conditions which are applied in steam cracking units, as presented in Figure 12 for the ACO™ technology developed by KBR Company.

Figure 12 – Olefins Recovery Section of ACO™ Technology by KBR Company (TALLMAN et. al., 2010)

The cryogenic processes applied to olefins recovery raises, even more, the capital requirement to petrochemical FCC units when compared with conventional FCCs, despite this, the growing market for petrochemicals and falling demand for transportation fuels, tends to compensate the higher investment.

Residue Fluid Catalytic Cracking (RFCC) Technologies – Dealing with Heavy Feeds

One variation of the fluid catalytic cracking that has been widely applied in the last years is the Residue Fluid Catalytic Cracking (RFCC). In this case, the feed stream to the process is basically the bottom stream from the atmospheric distillation column, called atmospheric residue, that have high carbon residue and higher contaminants content like metals, nitrogen, and sulfur.

Due to the feed stream characteristics, the residue catalytic cracking units require design and optimization changes. The higher levels of residual carbon in the feed stream led to higher temperatures in the catalyst regeneration step and a lower catalyst circulation rate to keep the reactor in constant temperature, this fact reduces the catalyst/oil ratio that leads to a lower conversion and selectivity. To avoid these effects, the RFCC units normally rely on catalyst coolers, as presented in Figure 13.

Figure 13 – Catalyst Cooler Process Arrangement for a Typical RFCC Unit (Handbook of Petroleum Refining Processes, 2004)

Installation of catalyst cooler system raises the process unit profitability through the total conversion enhancement and selectivity to noblest products as propylene and naphtha against gases and coke production, furthermore, helps the refinery thermal balance, once produces high-pressure steam. The use of catalyst cooler is also necessary when the unit is designed to operate under total combustion mode, in this case, the heat release rate is higher due to the total burn of carbon to CO2, as presented below.

C + ½ O2 → CO (Partial Combustion)  ΔH = - 27 kcal/mol

C + O2 → CO2 (Total Combustion)       ΔH = - 94 kcal/mol

In this case, the temperature of the regeneration vessel can reach values close to 760 oC, leading to higher risks of catalyst damage which is minimized through catalyst cooler installation. The option by the total combustion mode needs to consider the refinery thermal balance, once, in this case, will not the possibility to produce steam in the CO boiler, furthermore, the higher temperature in the regenerator requires materials with noblest metallurgy, this significantly raises the installation costs of these units.

As pointed earlier, the feed streams characteristics to RFCC units require modifications when compared with the conventional fluid catalytic cracking. The presence of higher content of nitrogen compounds leads to an accelerated process of catalyst deactivation through acid sites neutralization, the presence of metals like nickel, sodium, and vanadium raises the coke deposition on the catalyst and lead to a higher production of hydrogen and gases, besides that, reduces the catalyst lifecycle through the zeolitic matrix degradation. Beyond these factors, heavier feed streams normally have high aromatics content that are refractory to the cracking reactions, leading to a higher coke deposition rate and lower conversion.

Due to this operation conditions, the residue fluid catalytic cracking units presents higher catalyst consumption when compared with the conventional process, this fact raises considerably the operational costs of the RFCC units. However, the most modern units have applied specific catalysts to process residual feed streams, in this case, the catalyst has a higher porosity aiming to allow a better adaptation to the high aromatics content, furthermore, the catalyst needs to have a higher metals tolerance.

The control of contaminants content in the feed stream or his effects is a fundamental step to the residue fluid catalytic cracking process. Sodium content can be minimized through an adequate crude oil desalting process and the effects of nickel (dehydrogenation reactions) can be reduced by dosage of antimony compounds that act like neutralizing agent of the nickel dehydrogenation activity, reducing the generation of low added value gases, in its turn, the vanadium effects can be controlled through the addition of rare earth to the catalyst, like cerium compounds.  The addition of these compounds needs to be deeply studied once significantly raises the catalyst cost.

The use of visbreaking units to treat the feed streams to RFCC units  is a process scheme adopted by some refiners, in these cases, the most significant effect in the reduction in the residual carbon, however, due to his higher effectiveness, the tendency in the last decades is to treat the bottom barrels streams in deep hydrotreating or hydrocracking units before to pump for RFCC units, with this processing scheme it’s possible to achieve lower contaminants content, mainly metals, leading to a higher catalyst lifecycle.  Furthermore, the hydroprocessing has the advantage of the reduction of the sulfur content in the unit intermediate streams, minimizing the necessity or severity of posterior treatments, a clear disadvantage of this refining scheme is the high hydrogen consumption that significantly raises the operational costs.

Like to the conventional FCC units, the main operational variables to RFCC units are the reaction temperature, normally considered in the highest point in the reactor (also called riser), feed stream temperature, feed stream quality, feed stream flow rate and catalyst quality. It’s relevant to quote that the conventional FCC units can process atmospheric residue as the feed stream, however, it’s necessary to control the contaminants content, mainly metals, which requires processing lighter crudes with higher costs that raise the operational costs and reduces the flexibility of the refiner in relation of the crude oil supplier.

Some of the most relevant residue fluid catalytic cracking technologies available commercially are the R2R™ by Axens Company, the INDMAX™ process licensed by Lummus Company and the RxPro™ process developed by the UOP Company.  Figure 14 presents a block diagram showing a case study demonstrating how the petrochemical FCC unit, in this case the INDMAX™ technology by Lummus Company, can maximize the yield of petrochemicals in the refining hardware.

Figure 14 – Olefins Maximization in the Refining Hardware with INDMAX™ FCC Technology by Lummus Company (SANIN, A.K., 2017)

It’s interesting to note that, in the case presented in Figure 15 the refiner can maximize olefins production from atmospheric residue, as aforementioned, due to the feedstock characteristic is necessary to apply a residue hydrotreating unit upstream to the FCC unit (the RHDS unit) to control the contaminants content to the FCC catalyst.

Propylene Recovery Section

The growing demand by petrochemicals lead some refiners to install propylene recovery units aiming to allow the maximization of light olefins yield in his refining hardware. Among the light olefins, the propylene is one of the most relevant petrochemical intermediate due to the high demand and added value.

The propylene can be applied as intermediate to the production some fundamental products, for example:

·       Acrylonitrile;

·       Propylene Oxide;

·       Cumene;

·       Acrylic Acid;

·       Polypropylene;

Propylene can be produced through conventional processes like Steam Cracking and Fluid Catalytic Cracking (FCC) or through directed processes like metathesis of ethylene and butane, propane dehydrogenation, olefins cracking, Methanol to Olefins processes (MTO), among others. Currently a major part of the propylene market is supplied by steam cracking units, but close to 28 % of the global propylene demand is from the separation of LPG produced in Fluid Catalytic Cracking Units (FCC).

Normally, the LPG produced in FCC units contain close to 30 % of propylene and the added value of the propylene is close to 2,5 times of the LPG. According to the local market, the installation of propylene separation units presents an attractive return over investment. Despite the advantage, a side effect of the propylene separation from LPG is that the fuel stays heavier leading to specifications issues, mainly in colder regions, in these cases alternatives are to segregate the butanes and send this stream to gasoline pool, add propane to the LPG or add LPG from natural gas. It’s important take into account that some of these alternatives reduce the LPG offer, which can be a severe restriction according to the market demand.

A great challenge in the propylene production process is the propane and propylene separation step. The separation is generally hard by simple distillation because the relative volatility between propylene and propane is close of 1.1. This fact generally conducts to distillation columns with many equilibrium stages and high internal reflux flow rates.

There are two technologies normally employed in propylene-propane separation towers that are known as Heat-Pump and High-Pressure configurations.

The high-pressure technology applies a traditional separation process that uses a condenser with cooling water to promotes the condensation of top products, in this case, it’s necessary to apply sufficient pressure to promote the condensation of products in the ambient temperature. Furthermore, the reboiler uses steam or another available hot source. The adoption of high-pressure separation route requires a great availability of low-pressure steam in the refining hardware, in some cases this can be a restrictive characteristic and the heat pump configuration is more attractive, despite the higher capital requirements.

The application of heat pump technology allows decrease the operating pressure by close of 20 bar to 10 bar, this fact increase the relative volatility propylene-propane, making the separation process easier and, consequently, reducing the number of equilibrium stages and internal reflux flow rate required for the separation.

Normally, when the separation process by distillation is hard (with relative volatilities lower than 1.5) the uses of heat pump technology show more attractive.

Furthermore, some variables need to be considerate during the choice of the best technology for the propylene separation process like availability of utilities, temperature gap in the column and installation cost.

Normally, the propylene is produced in the refineries with to specifications. The polymer grade that is most common and have higher added value with a purity of 99,5 % (minimum) this grade is directed to polypropylene market. The chemical grade where the purity varies between 90 to 95% is normally directed to other uses. A complete process flow diagram for a typical propylene separation unit applying heat pump configuration is presented in Figure 15.

Figure 15 – Typical Process Flow Diagram for an FCC Propylene Separation Unit Applying Heat Pump Configuration

The LPG from FCC unit is pumped to a depropanizer column where the light fraction (essentially a mixture of propane and propylene) is recovered in the top of the column and sent to a deethanizer column while the bottom (butanes) is pumped to LPG or gasoline pool, according to the refining configuration. The top stream of the deethanizer column (lighter fraction) is sent back to FCC where is incorporated to refinery fuel gas pool, or in some cases can be directed to petrochemical plants to recover the light olefins (mainly ethylene) present in the stream while the bottom of the deethanizer column is pumped to the C3 splitter column, where the separation of propane x propylene is carried out. The propane recovered in the bottom of the C3 splitter is sent to LPG pool where the propylene is sent to propylene storage park. The feed stream passes through a caustic wash treating aiming to remove some contaminants that can lead to deleterious effect to petrochemical processes, an example is the carbonyl sulfide (COS) that can be produced in the FCC (through the reaction between CO and S in the Riser).

As aforementioned, face the current trend of reduction in transportation fuels demand at the global level, the capacity of maximum adding value to crude oil can be a competitive differential to refiners. Due to the high capital investment needed for the implementation that allows the conventional refinery to achieve the maximization of chemicals, capital efficiency becomes also an extremely important factor in the current competitive scenario as well as the operational flexibility related to the processed crude oil slate.

Although the advantages presented by closer integration between refining and petrochemical assets, it’s important to understand that the players of downstream industry are facing with a transitive period where, as presented in Figure 1, the transportation fuels are responsible by great part of the revenues. In this business scenario, it’s necessary to define a transition strategy where the economic sustainability achieved by the current status (transportation fuels) needs to be invested to build the future (maximize petrochemicals). Keep the eyes only in the future or only in the present can be a competitive mistake.

The Combination of FCC and Steam Cracking Units – Maximum Olefins Yield

As aforementioned, maximize the light olefins yield in the refining hardware can be an attractive way to ensure competitiveness in the downstream market according to the recent forecasts. The combination of FCC and steam cracking units in the refining hardware can be an alternative to achieve this goal. Table 2 presents a comparison between steam cracking and FCC technologies.

The characteristics of the FCC and steam cracking units allows high yield of olefins in the refining without competition for feedstocks, once the FCC is a bottom barrel conversion technology based in carbon rejection that applies mainly gasoil as feed stream while the steam cracking process produces mainly ethylene through thermal cracking of ethane and high paraffinic naphtha.

The yield of propylene in the steam cracking units relies on the feedstock quality, being higher in units processing naphtha. In the last years some refiners are adopting the ethane as main feedstock due to his lower prices, this fact reduces the propylene offer from steam crackers, raising the relevance of the propylene from FCC units to ensure the market supply.  This fact has been the main driver to the growing of propylene on purpose technologies like propane dehydrogenation, methanol to olefins, and metathesis. Despite this recent trend, the steam cracking units remain the main propylene source to the market with close to 48 % of the market.

An example of refining configuration relying on FCC and steam cracking units is presented in Figure 16.

Figure 16 – Integrated Refining Scheme Base on FCC and Steam Cracking Units (UOP, 2019) Source: Honeywell UOP - www.uop.honeywell.com

Considering the recent trend of reduction in transportation fuels demand followed by the growth of petrochemicals market makes the synergy between FCC and steam cracking units an attractive way to maximize the petrochemicals production in the refining hardware.

As aforementioned, face the current trend of reduction in transportation fuels demand at the global level, the capacity of maximum adding value to crude oil can be a competitive differential to refiners. Due to the high capital investment needed for the implementation that allows the conventional refinery to achieve the maximization of chemicals, capital efficiency becomes also an extremely important factor in the current competitive scenario as well as the operational flexibility related to the processed crude oil slate.

The Role of FCC Technologies in the Crude Oil to Chemicals Strategy

Due to the increasing market and higher added value as well as the trend of reduction in transportation fuels demand, some refiners and technology developers has dedicated his efforts to develop crude to chemicals refining assets. One of the big players that have been invested in this alternative is the Saudi Aramco Company, the concept is based on the direct conversion of crude oil to petrochemical intermediates as presented in Figure 17.

Figure 17 – Saudi Aramco Crude Oil to Chemicals Concept (IHS Markit, 2018)

The process presented in Figure 17 is based on the quality of the crude oil and deep conversion technologies like High Severity or petrochemical FCC units and deep hydrocracking technologies, in this case it’s interesting to note the added value to the processed crude through the synergy of FCC and naphtha steam cracking units.

Another great refining technology developers like UOP, Shell Global Solutions, ExxonMobil, Axens, and others are developing crude to chemicals technologies, reinforcing that this is a trend in the downstream market. Figure 18 presents a highly integrated refining configuration capable to convert crude oil to petrochemicals developed by UOP Company.

Figure 18 – Integrated Refining Configuration Based in Crude to Chemicals Concept by UOP Company. Source: Honeywell UOP - www.uop.honeywell.com

As presented in Figure 18, the production focus change to the maximum adding value to the crude oil through the production of high added value petrochemical intermediates or chemicals to general purpose leading to a minimum production of fuels. As aforementioned, big players as Saudi Aramco Company have been made great investments in COC technologies aiming to achieve even more integrated refineries and petrochemical plants, raising considerably his competitiveness in the downstream market. The major technology licensors as Axens, UOP, Lummus, Shell, ExxonMobil, etc. has been applied resources to develop technologies capable to allow a closer integration in the downstream sector aiming to allow refiners extract the maximum added value from the processed crude oil, an increasing necessity in a scenario where the refining margins are under pressure.

It’s important to consider that the cost composition evolves several factors, and this scenario can be different according to the local business environment. Figure 19 present a comparison between the petrochemicals yields of traditional refineries, a benchmark integrated refinery and crude to chemicals complexes, according to data from Wood Company.

Figure 19 – Petrochemicals Yield Comparison (Wood Company, 2024)

Analyzing Figure 19 it’s possible to note the higher added value reached in crude to chemicals refineries when compared even with highly integrated refineries.

Although the advantages presented by closer integration between refining and petrochemical assets, it’s important to understand that the players of downstream industry are facing with a transitive period where, as presented in Figure 1, the transportation fuels are responsible by great part of the revenues. In this business scenario, it’s necessary to define a transition strategy where the economic sustainability achieved by the current status (transportation fuels) needs to be invested to build the future (maximize petrochemicals). Keep the eyes only in the future or only in the present can be a strategic mistake.

As described above, the fluid catalytic cracking units can ensure operational flexibility and higher refining margins for the downstream players under the challengeful scenario imposed to the fossil fuels and is expected growing investments in FCC installations for the next years. Based on data from GlobalData Company, the global installed fluid catalytic cracking capacity will raise from 14,4 million barrels per day (MMbpd) in 2022 to 15,8 MMbpd in 2026, a growth of 9,3 % in four years. Figure 20 presents an overview of the growth of FCC installed capacity for the next years.

Figure 20 – Growth of Global FCC Installed Capacity 2022 to 2026 (GlobalData Company, 2022)

As expected, the growth of FCC capacity will lead by the Asian players which presents highest integration capacity among the downstream players and have been investing heavily to maximize the petrochemicals yield in their refining assets, including crude to chemicals refineries. The Asian players will add close to 900 thousand barrels per day (Mbd) to the global FCC processing capacity until 2026 followed by the African players, which have been invested in FCC as part of their strategy to reduce the external dependence from high quality gasoline, in other words, differently of Asian players the addition of global FCC capacity produced by African players tends to be related to conventional and low severity FCC units with the gasoline production focus especially leaded by the new Dangote refinery in Nigeria, the Africans players will add close to 570 Mbd to the global FCC processing capacity until 2026.

Conclusion

The synergy between refining and petrochemical processes raises the availability of raw material to petrochemical plants and makes the supply of energy to these processes more reliable at the same time ensures better refining margin to refiners due to the high added value of petrochemical intermediates when compared with transportation fuels. Another advantage is the reduction of risks of transportation fuels oversupply, facing the current scenario of demand reduction and restriction of fossil fuels, this scenario is even faced in some markets.

It’s important to consider that integrated processes lead to higher operational complexity, however, given current and middle term scenarios to the refining industry, better integration between refining and petrochemical processes is fundamental to the economic sustainability of the downstream industry. In this scenario, Petrochemical FCC units can ensure a significant competitive advantage to refiners inserted in markets with high demand by petrochemicals, despite the higher capital spending in comparison with conventional FCC units. Again, it’s important to understand the transitive period faced by the downstream industry and maintain competitive operations with the current focus in transportation fuels while the transition to petrochemicals is prepared in a sustainable manner aiming to keep economic sustainability and competitiveness in the downstream market, and even the refiners with restriction of capital investment can found relatively low cost alternatives to optimize their FCC units to improve the added value to the processed crude oil and the competitiveness in the market. Finally, considering the current scenario and recent forecasts, a refining hardware able to maximize olefins can be powerful tool to refiners in order to keep competitiveness and relevance in the downstream market. The relevance of FCC units for the future of the downstream industry is shown by the significant growth of global FCC processing capacity which is expected to reach 15,8 MMbpd in 2026 with 9,3 % of growth in comparison to 2022, as expected this growth will lead by the Asian players which present highest integration level between refining and petrochemical assets among the downstream players.

References

Advances in Catalysis for Plastic Conversion to Hydrocarbons – The Catalyst Group (TCGR), 2021.

GARY, J. H.; HANDWERK, G. E. Petroleum Refining – Technology and Economics.4th ed. Marcel Dekker., 2001.

GELDER, A.; BAILEY, G. The Future of Petrochemicals: A Tale of Two Transitions, Wood Mackenzie, 2020.

Global Capacity and Capital Expenditure Outlook for Refineries – Global Data Company, 2022.

LAMBERT, N.; OGASAWARA, I.; ABBA, I.; REDHWI, H.; SANTNER, C. HS-FCC for Propylene: Concept to Commercial Operation. PTQ Magazine, 2014.

LIU, S.; KOTS, P.A.; VANCE, B.C.; DANIELSON, A.; VLACHOS, D.G. Plastic Waste to Fuels by Hydrocracking at Mild Conditions, Science Advances, 2021.

MALLER, A.; GBORDZOE, E. High Severity Fluidized Catalytic Cracking (HS-FCC™): From concept to commercialization – Technip Stone & Webster Technical Presentation to REFCOMM™, 2016.

MYERS, R.A. Handbook of Petroleum Refining Processes. 3a ed. McGraw-Hill, 2004.

Refinery-Petrochemical Integration (Downstream SME Knowledge Share). Wood Mackenzie Presentation, 2019.

ROBINSON, P.R.; HSU, C.S. Handbook of Petroleum Technology. 1st ed. Springer, 2017.

SALGADO, H. Controlling the metals content of FCC equilibrium catalyst. PTQ Magazine, Q3 2018.

SARIN, A.K. – Integrating Refinery with Petrochemicals: Advanced Technological Solutions for Synergy and Improved Profitability – Presented at Global Refining & Petrochemicals Congress (Mumbai, India), 2017.

SILVA, M. W. – More Petrochemicals with Less Capital Spending. PTQ Magazine, 2020.

TALLMAN, M. J.; ENG, C.; SUN, C.; PARK, D. S. - Naphtha Cracking for Light Olefins Production. PTQ Magazine, 2010.

Dr. Marcio Wagner da Silva is Process Engineering Manager at a Crude Oil Refinery based in São José dos Campos, Brazil. He earned a bachelor’s in chemical engineering from the University of Maringa (UEM), Brazil and a PhD. in Chemical Engineering from the University of Campinas (UNICAMP), Brazil. He has extensive experience in research, design and construction in the oil and gas industry, including developing and coordinating projects for operational improvements and debottlenecking to bottom barrel units, moreover Dr. Marcio Wagner earned an MBA in Project Management from the Federal University of Rio de Janeiro (UFRJ), and in Digital Transformation at Pontifical Catholic University of Rio Grande do Sul (PUC/RS), in Production and Operations Management at University of Sao Paulo (USP), and is certified in Business from Getulio Vargas Foundation (FGV).