Higher Added Value to the Processed Crude – The Hydrocracking Technologies

Introduction and Context

???????????The necessity to reduce the environmental impact and the higher sustainability of the industrial processes normally is translated in stricter regulations and higher control upon the industries activities, mainly to those that have a high environmental footprint as the crude oil production chain. This fact is positive and welcome, in view of the necessity to preserve the natural resources and the needed technological development to meet these regulations.

???????????One of the most impacting regulations to the downstream industry is the necessity to reduce the sulfur content in the maritime fuels, known as IMO 2020, this regulation established which from the maximum sulfur content in the maritime transport fuel oil (Bunker) is 0,5 % (m.m) against the previously 3,5 % (m.m). The main objective is to reduce the SOx emissions from maritime fleet, significantly decreasing the environmental impact of this business. ?

???????????The marine fuel oil, known as bunker, is a relatively low viscosity fuel oil applied in diesel cycle engines to ships movement. Before 2020, the bunker was produced through the blending of residual streams as vacuum residue and deasphalted oil with dilutants like heavy gasoil and light cycle oil (LCO), due to the new regulation, a major part of the refiners will not be capable to produce low sulfur bunker through simple blend.

???????????Due be produced from residual streams with high molecular weight, there is a tendency of contaminants accumulation (sulfur, nitrogen, and metals) in the bunker, this fact makes difficult meet the new regulation without additional treatment steps, what should lead to increasing the production cost of this derivative and the necessity to modifications in the refining schemes of some refineries. Figure 1 presents a schematic diagram of how the bunker was produced before the IMO 2020.

Figure 1 – Bunker Production Process before IMO 2020

???????????The drastic reduction of sulfur content in the final product, lead refiners to look for alternatives to reduce the sulfur content in the intermediate streams, and this is a hard task to refiners processing heavy and extra-heavy crudes.

???????????Beyond the necessity to add value to bottom barrel streams in compliance with the IMO 2020, the increasingly restrict environmental regulations requires even more capacity to produce cleaner distillates, imposing another challenge to refiners processing extra-heavy crudes. The growing trend of petrochemical integration is another great challenge to refiners with access to extra-heavy crudes once requires more complex and expensive refining hardware, in this sense, the hydrocracking and deep hydrocracking technologies can be a fundamental tool to allow the refiners with high capital investment capacity to reach a highlighted competitive positioning in the downstream market through adequate balance of bottom barrel conversion capacity and petrochemicals maximization.

???????????The COVID-19 pandemic reduces the spread between the 0,5 % sulfur and 3,5 % sulfur marine fuel oil in 88 %, from 321,50 US$/ ton in January of 2020 to 38,0 US$/ton in June at the same year, as presented in Figure 2, based on data from S&P Global Platts Company.

Figure 2 – VLFSO and HSFO Fuel oil Spreads (S&P Global Platts, 2021)

???????????Despite this fall in the spread, it’s important to considering the increasingly stricter regulations and the trend of reduction of the HSFO market in the middle term (as presented in Figure 3), this fact plus the trend of reduction in transportation fuels demand and growing demand of petrochemicals at global level tends to favor refiners relying on most complex refining hardware that are capable to processing heavy crude oils and maximize the added value to the processed crude.?

Figure 3 – Growing Participation of VLFSO in the Bunker Market (IEA, 2021)

Processing Extra Heavy Crudes – The Hydrocracking Alternative

Refiners processing heavy and extra-heavy (or high sulfur) crudes face a great challenge to meet the IMO 2020 once is extremely difficult to comply with the new regulation through carbon rejection technologies, in this case, the hydrogen addition technologies are fundamental.

The hydroprocessing of residual streams presents additional challenges when compared with the treating of lighter streams, mainly due to the higher contaminants content and residual carbon (RCR) related with the high concentration of resins and asphaltenes in the bottom barrel streams. Figure 4 shows a schematic diagram of the residue upgrading technologies applied according to the metals and asphaltenes content in the feed stream.?

Figure 4 – Residue Upgrading Technologies According to the Contaminants Content (Encyclopedia of Hydrocarbons, 2006)

???????Higher metals and asphaltenes content led to a quick deactivation of the catalysts through high coke deposition rate, catalytic matrix degradation by metals like nickel and vanadium or even by the plugging of catalyst pores produced by the adsorption of metals and high molecular weight molecules in the catalyst surface. By this reason, according to the content of asphaltenes and metals in the feed stream are adopted more versatile technologies aiming to ensure an adequate operational campaign and an effective treatment.

As exposed above, extra-heavy crude oils or with high contaminants content can demand deep conversion technologies to meet the new quality requirements to the bunker fuel oil. Hydrocracking technologies are capable to achieve conversions higher than 90% and, despite, the high operational costs and installation can be attractive alternatives.

The hydrocracking process is normally conducted under severe reaction conditions with temperatures that vary to 300 to 480 oC and pressures between 35 to 260 bar. ?Due to process severity, hydrocracking units can process a large variety of feed streams, which can vary from gas oils to residues that can be converted into light and medium derivates, with high value added.

?Figure 5 shows a typical process arrangement to hydrocracking units with two reaction stage and intermediate gas separation, adequate to treat high streams with high contaminants content. ?

Figure 5 – Typical Arrangement for Two Stage Hydrocracking Units with Intermediate Gas Separation

???????????The residue produced by hydrocracking units have low contaminants content, able to be directed to the refinery fuel oil pool aiming to produce low sulfur bunker, allowing the market supply and the competitiveness of the refiners.

The process shown in Figure 5 presents a fixed bed hydrocracking unit, to heavier crudes, this unit can be inadequate due to the low operating life cycle, in this case the ebulated bed and slurry phase reactors can be more effective, despite the higher capital spending.?The capital requirement is one of the most restriction to refiners in adopt the hydrocracking technologies both to capital and operating capital due to the necessity of larger hydrogen generation units, catalysts costs, etc. Figure 6 presents a comparison between residue upgrading alternatives related to the capital investment (CAPEX) and effectiveness in the bottom barrel processing.

Figure 6 – Capital Spending x Residue Conversion to Residue Upgrading Technologies (Shell Catalysts and Technologies, 2019)

???????????As presented in Figure 6, the hydrocracking technologies present the higher level of required capital spending, on the other side offer the higher conversion to bottom barrel streams, a necessity to refiners processing heavy and extra-heavy crudes. According to Figure 3, the other alternatives are not effective to treating residue streams with high carbon residue and metals, common characteristics of extra-heavy crude oils. In this case, the hydrocracking alternative is the most technically adequate solution.

Deep Hydrocracking Technologies – Recovering More Added Value from the Crudes

As aforementioned, despite the high performance, the fixed bed hydrocracking technologies can be not economically effective to treat residue from heavy and extra-heavy due to the short operating lifecycle. Technologies that use ebullated bed reactors and continuum catalyst replacement allow higher campaign period and higher conversion rates, among these technologies the most known are the H-Oil and Hyvahl? technologies developed by Axens Company, the LC-Fining Process by Chevron-Lummus, and the Hycon? process by Shell Global Solutions. These reactors operate at temperatures above of 450 oC and pressures until 250 bar. Figure 7 presents a typical process flow diagram for a LC-Fining? process unit, developed by Chevron Lummus Company while the H-Oil? process by Axens Company is presented in Figure 8.

Figure 7 – Process Flow Diagram for LC-Fining? Technology by CLG Company (MUKHERJEE & GILLIS, 2018)

Catalysts applied in hydrocracking processes can be amorphous (alumina and silica-alumina) and crystalline (zeolites) and have bifunctional characteristics once the cracking reactions (in the acid sites) and hydrogenation (in the metals sites) occurs simultaneously.?

Figure 8 – Process Flow Diagram for H-Oil? Process by Axens Company (FRECON et. al, 2019)

An improvement in relation of ebullated bed technologies is the slurry phase reactors, which can achieve conversions higher than 95 %. In this case, the main available technologies are the HDH? process (Hydrocracking-Distillation-Hydrotreatment), developed by PDVSA-Intevep, VEBA-Combicracking Process (VCC)? commercialized by KBR Company, the EST? process (Eni Slurry Technology) developed by Italian state oil company ENI, and the Uniflex? technology developed by UOP Company. Figure 9 presents a basic process flow diagram for the VCC? technology by KBR Company.

Figure 9 – Basic Process Arrangement for VCC? Slurry Hydrocracking by KBR Company (KBR Company, 2019)

???????????In the slurry phase hydrocracking units, the catalysts in injected with the feedstock and activated in situ while the reactions are carried out in slurry phase reactors, minimizing the reactivation issue, and ensuring higher conversions and operating lifecycle. Figure 10 presents a basic process flow diagram for the Uniflex? slurry hydrocracking technology by UOP Company.

Figure 10 – Process Flow Diagram for Uniflex? Slurry Phase Hydrocracking Technology by UOP Company (UOP Company, 2019).

???????????Other commercial technologies to slurry hydrocracking process are the LC-Slurry? technology developed by Chevron Lummus Company and the Microcat-RC? process by Exxon Mobil Company. Figure 11 presents a basic process flow diagram for the LC-Slurry? technology developed by Lummus Company.

Figure 11 – Basic Process Arrangement for LC-Slurry? Technology developed by Lummus Company (BISWAS et. al., 2017)

Aiming to meet the new bunker quality requirements, noblest streams, normally directed to produce middle distillates can be applied to produce low sulfur fuel oil, this can lead to a shortage of intermediate streams to produce these derivatives, raising his prices. The market of high sulfur content fuel oil should strongly be reduced, due to the higher prices gap when compared with diesel, his production tends to be economically unattractive.

Synergy between Delayed Coking and Hydrocracking Units

???????????Some refining configurations considering the combination of delayed coking and hydrocracking technologies to ensure high bottom barrel conversion capacity, ensuring minimum fuel oil production. Figure 12 present a block diagram for Coking/Hydrocracking refining scheme.?

Figure 12 – Process Arrangement to a Refinery Operating Under Coking/Hydrocracking Configuration

???????????In the case of Coking/Hydrocracking refining scheme, fuel oil production is reduced to the minimum necessary to attend the consumer market, delayed coking and hydrocracking units raise the production of high added value products, like naphtha, diesel and Jet fuel, leading to a significant rise in the refiner profitability. ?

???????????The improving in the refinery conversion grade rises the complexity of the refining scheme and, despite improve the profitability, operational costs also are higher to more complex refineries, however, the higher volume and better quality of the produced derivatives produces sufficient elevation in the refining margin to cover these additional costs. ?

???????????In the refining configuration shown in Figure 12, sending the heavy and light coker gas oil to hydrocracking unit it’s possible to produce high quality middle distillates like diesel and jet fuel that are high demand and added value derivatives. Figure 13 presents an estimated yield considering the combination of deep hydrocracking unit (LC-Fining by Chevron-Lummus Company) and a Delayed Coking Unit.

Figure 13 – Estimated Yields for Bottom Barrel Conversion Units (Chevron-Lummus Company, 2018)

As presented in Figure 13, it’s possible to achieve a highlighted deep bottom barrel conversion through the synergy of Delayed Coking and Hydrocracking units. The combination of hydrogen addition and carbon rejection technologies like hydrocracking and delayed coking ensures high capacity to processing heavy and discounted crudes leading to an important competitive advantage to refiners. Despite the high bottom barrel conversion profile achieved through the synergy between hydrocracking and delayed coking technologies, there are some attention points related to the raise of cracked feeds proportion in the feedstock to hydrocracking units.

Deep Conversion Refining Hardware – Petrochemicals from Bottom Barrel Streams

???????????As aforementioned the residue upgrading units are capable to improve the quality of bottom barrel streams, the main advantage of the integration between residue upgrading and petrochemical units like steam cracking is the higher availability of feeds with better crackability characteristics.

???????????Bottom barrel streams tend to concentrate aromatics and polyaromatics compounds that present uneconomically performance in steam cracking units due the high yield of fuel oil that presents low added value, furthermore, the aromatics tends to suffer condensation reaction in the steam cracking furnaces, leading to high rates of coke deposition that reduces the operation lifecycle and raises the operating costs. In this case deep conversion units like hydrocracking can offer higher operational flexibility.

Once cracking potential is better to paraffinic molecules, and the hydrocracking technologies can improve the H/C in the molecules converting low added value bottom streams like vacuum gasoil to high quality naphtha, kerosene, and diesel the synergy between hydrocracking and steam cracking units, for example, can improve the yield of petrochemical intermediates in the refining hardware, an example of highly integrated refining configuration relying on hydrocracking is presented in Figure 14.

Figure 14 – Integrated Refining Scheme Relying on Residue Upgrading and Petrochemical Maximization Technologies (UOP, 2019)

???????????Considering the recent trend of reduction in transportation fuels demand followed by the growth of petrochemicals market makes the presence of hydrocracking units in the refining hardware raise the availability of high-quality intermediate streams capable to be converted into petrochemicals, an attractive way to maximize the value addition to processed crude oil in the refining hardware. As presented in Figure 14, the synergy between carbon rejection and hydrogen addition technologies like FCC and hydrocracking units can offer an attractive alternative, sometimes the hydrocracking and FCC technologies are faced by competitors technologies in the refining hardware due to the similarities of feed streams that are processed in these units. In some refining schemes, the mild hydrocracking units can be applied as pretreatment step to FCC units, especially to bottom barrel streams with high metals content that are severe poison to FCC catalysts, furthermore the mild hydrocracking process can reduce the residual carbon to FCC feed, raising the performance of FCC unit and improving the yield of light products like naphtha, LPG, and olefins.

Considering the great flexibility of deep hydrocracking technologies that are capable to convert feed stream varying from gas oils to residue, an attractive alternative to improve the bottom barrel conversion capacity is to process in the hydrocracking units the uncracked residue in FCC unit aiming to improve the yield of high added value derivatives in the refining hardware, mainly middle distillates like diesel and kerosene.

??????????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 Side Effect of Cracked Feeds – A Special Challenge to Hydrocracking Units

???????????The most common cracked feeds directed to hydrocracking units are residual streams from FCC like Light Cycle (LCO) and Decanted Oil (DO) and Heavy Coker Gasoil (HCGO) from Delayed Coking units. Another less common feed is residue from Visbreaking units.

???????????The main characteristics that influence in the hydrocracking performance for each feedstock is presented below:

·??????FCC Cycle Oils – Present high aromaticity that are normally refractory to cracking reactions as well as refractory sulfur components, raising the sulfur content in the final products and reduction in diesel cetane number, on the other side, normally presents low basic nitrogen content that is a poison to the hydrocracking catalysts.

·??????Thermal Cracking Feeds – Normally presents low aromatics content but concentrate refractory sulfur components.

The Heavy Coker Gasoil (HCGO) is an interesting case study as a feed to hycrocracking unit. Refiners with high complexity refining hardware can rely on the synergy between delayed coking and hydrocracking technologies to ensure added value to bottom barrel streams.

The quality of the HCGO relies on the quality of the feed to the delayed coking unit as well as the operating mode of the unit, mainly the recycle ratio. Higher recycle ratios produces better quality HCGO once reduces Conradson Carbon Residue (CCR), reducing the contaminants content like metals, sulfur, and nitrogen.

?????????????Despite this advantage, the delayed coking operators normally minimize the recycle ratio to minimum as possible aiming to raise the fresh feed processing capacity and the quality of HCGO is not an optimization focus of the refinery. For this reason, normally the HCGO is a hard feed to hydrocracking units due to the high content of refractory sulfur components, high CCR, high nitrogen content, and aromatics concentration.

?????????????The sulfur and nitrogen content raises the heat release in the first bed (Higher exothermal profile) that can produce damage to the catalysts, the nitrogen tends to inhibit the cracking reaction leading to lower conversion in the unit. Hydrocracker’s processing feeds with high nitrogen content tends to apply processing configuration with intermediate gas separation to control the catalyst activity. The higher production of H2S and NH3 due to the higher concentration of sulfur and nitrogen reduces the hydrogen partial pressure, raise the necessity of wash water to the units, and can raise the corrosion rate in the processing unit.

?????????????Aromatics compounds tend to raise the hydrogen consumption, the heat release in the catalyst bed, and are precursors of coking deposition that deactivate the catalyst. Other side effects of the cracked feeds to hydrocracking units are the impact over the quality of the final products like lower cetane number of diesel, higher smoke point of kerosene, lower viscosity index in the lubricating oils and higher sulfur content.

????????????As described above, processing cracked feeds in hydrocracking units present some additional challenges to refiners related to hydrogen consumption, better quench design of the catalyst bed due to the higher exothermic profile of the reactions, and lower global activity of the catalyst due to the higher poison content, like basic nitrogen. These characteristics lead the refiners processing cracked feeds in hydrocracking units to invest more capital in feed treating systems like filtering and guard beds, despite this apparent disadvantage, refiners able to add value to bottom barrel streams can enjoy highly competitive advantage considering the downstream market post IMO 2020. For refiners processing extra-heavy bottom barrel streams, the deep hydrocracking technologies like slurry phase hydrocracking can be an interesting option, despite the high capital and operating costs.

Conclusion

???????????Comply with IMO 2020 put under pressure the refining margins of low complexity refineries and reduced conversion capacity, once there is the tendency to raise the prices of low sulfur crude oils, furthermore, the higher operational costs depending on the technological or optimization solution adopted by the refiner. The challenge is even harder to refiners processing heavy and extra-heavy crudes, in this case, despite the high capital spending the hydrocracking technologies can offer an attractive alternative, beyond this, hydrocracking technologies appears like a fundamental enabler to ensure high conversion of bottom barrel streams, especially considering the growing trend of integration between refining and petrochemical assets. For refiners processing low sulfur crudes, the solvent deasphalting technologies can be an attractive way to comply with IMO 2020.

The downstream industry faces a transitive period with deep changes in the consumer market where the necessity to decarbonize the energy matrix requires a increasing participation of renewables in the crude oil refineries and the technology development like electric vehicles and 3 D printing have great potential to destroy transportation fuels demand, leading to deep changes in the production profile of crude oil refineries. Stricter regulations like IMO 2020 raises, even more, the relevance of the residue upgrading capacity to the competitiveness in the downstream industry, creating pressure over the refiners with low complexity refining hardware, in this sense, refiners with high capital investment capacity are looking for closer integration with petrochemical assets as a strategy to reduce costs and improve revenues.

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, in other words, our current operations will sustain our desired future.

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