S. ABDUL WAHAB ALI, A. S. GHADEER and A. A. RODRIGUEZ SARMIENTO, Saudi Aramco, Dhahran, Saudi Arabia.
This article elaborates on the startup challenges of a refinery heavy naphtha reforming unit, which started in an alternative direction than the original design intent. It includes the elaboration of the unprecedented challenges faced during startup, leading to high coke content on continuous catalyst regeneration (CCR) reforming catalyst beyond the design limits, necessitating an innovative approach apart from traditional regneration protocols to regenerate highly coked catalyst without operational reforming reactors and hydrogen (H2) lifting gas.
Despite technical hurdles, the innovative solution enabled successful catalyst regeneration, reducing coke content from around 12 wt% to 0.2 wt% without costly ex-situ regeneration and restored unit functionality and successfully yielding financial benefit through innovative engineering to non-standard scenarios.
Background. The Saudi Aramco Jazan Refinery Complex (JZRC) is a full conversion oil refinery with 400,000 barrels per stream day (bpsd) nominal capacity to process Arabian crude, integrated with a 3.8 gigawatt (GW) vacuum residue (VR) gasification power block, called the Jazan Integrated Gasification and Power Co. (JIGPC), which produces H2, steam and other necessary utilities like nitrogen, oxygen (O2), etc., to sustain the refinery’s operation, as elaborated in FIG. 1.
The refinery has multiple hydroprocessing and conversion units to meet Saudi Arabia’s fuel demand and export petrochemical building blocks benzene and paraxylene. Naphtha hydrotreating (NHT), heavy naphtha reforming and its continuous catalyst regeneration (REF/CCR) is a part of the gasoline block operating area at Jazan Refinery, as shown in FIG. 2.
The purpose of this unit is to produce an aromatic rich reformed naphtha cut (reformate) and a H2-rich gas that is consumed by naphtha and diesel hydrotreaters (NHT and DHT), light naphtha isomerization (LN ISOM) and aromatics processing units within the refinery. The feed to this operating area is a compensation of sour straight run naphtha from the crude distillation unit (CDU), cracked naphtha from the hydrocracker (HCK), as well as imported naphtha from an outside supplier. Due to the presence of contaminants (organic nitrogen and sulfur), hydroprocessing of reformer feed in the NHT is always necessary to meet final product quality and environmental regulations, as well as the health of the downstream catalytic processes [affected by catalyst poisons (e.g., sulfur, nitrogen, metals, etc.)].
Alternative startup scheme. The original startup plan of Jazan refinery’s hydroprocessing units was based on H2 availability from JIGPC to start the NHT followed by CCR and other downstream-dependent units. Due to commissioning and startup delays on the JIGPC side—influenced by the COVID-19 pandemic—the refinery part of the complex approached the commissioning stage earlier, while the refinery startup was dependent on the JIGPC side startup. Hence, the unit was started up with an alternative startup scheme than the design intent, as shown in FIG. 3.
As indicated in FIG. 3, the reforming unit was started with imported H2 and sweet naphtha, followed by NHT unit startup with CCR-produced H2 to suffice for sweet naphtha production from the NHT as a feed to the CCR unit.
Reformer catalyst circulation/regeneration principle. Typically, to maintain the stable coke content of the catalyst within the reformer reactors, catalyst circulation is carried out by utilizing a lift gas system generally composed of five lift lines, which are responsible to transfer the catalyst between the reactors and also between the reaction section [H2 + hydrocarbon (HC) atmosphere] and regeneration section (O2 atmosphere), based on differential pressure between the bottom of each reactor to the top of the following reactor, then from the bottom of the last reactor (4th) to the top of the regenerator, as shown in FIG. 4.
The catalyst flows downward through the regenerator and each reactor vessel by gravity force. As the catalyst flows downwards into the reactors and regenerator vessels, it is transferred to the catalyst circulation circuit and later to the next reactor or regenerator vessel, using lift gas in an upward push in lift gas vessels. To achieve a normal lifting philosophy, an optimum differential pressure is required between the bottom of the reactor and the top of the following vessel to have enough of a driving force to lift properly.
The CCR reactor sections consist of a H2 environment due to H2 production from reforming reactions, while the regeneration section comprises an O2 and nitrogen environment to ensure the coke burning process. As both sections are operated at high temperatures, the mixing of one environment with another can have catastrophic results. Based on these factors, two lift gas media have been utilized accordingly for lifting purposes and to avoid the mixing of the two different environments.
Catalyst regeneration is performed in two main operating modes based on the coke level on the catalyst during regeneration startup to maintain proper burning and temperature profile across burning beds. Both modes can be activated either by an operator or automatically by ESD logic.
Each mode is described briefly in the following sections.
Black burn. This mode is typically used during the initial startup and when there is a possibility of having coke slippage out of the second burning bed for any upset reason. So, O2 in both oxychlorination and calcination zones must be stopped to prevent combustion of coked catalyst pills in these zones to prevent bed internals and catalyst integrity from any potential damage by uncontrolled exothermic reactions.
White/standard burn. This is the normal operating/standard mode, where spent catalyst complete coke combustion is achieved in burning beds and catalyst free of coke is present in oxychlorination and calcination zones. During white burn mode, the oxychlorination zone and calcination zone operate within their normal oxygen concentrations, while acidic and metallic dispersion on catalyst is carried out with an injection of a chlorinated agent.
Startup challenges and limitations. Although the initial intent for starting the CCR reformer reactor section to produce H2 was achieved, other limitations and sytematic challenges unfold in later stages for first time commissioning and startup of the unit. Firstly, the downstream compressor, which was essential for boosting the produced H2-rich gas from the reformer for catalyst circulation and provides the feed to the downstream H2 purification-pressure swing adsorber (PSA) unit, faced multiple mechanical issues during mechanical run tests (MRTs), including but not limited to, mechanical seal failures, anti-surge valves blockage and other instrumentation faults.
Secondly, the downstream PSA also faced some instrumentation failures on the malfunctioned feed flow transmitter, which prevented accruate H2 flow and hindered the unit tuning. Additionally, compounding these issues—even after pure H2 supply to the NHT unit, essential for feeding the pre-treated sweet naphtha to the reformer and releasing the dependency from imported sweet naphtha—could not stabilize due to repeated failures of the NHT unit’s recycle gas compressor, caused by motor design flaws resulting in tripping on high amperes.
During startup study evaluations, the team estimated a maximum of two weeks operation of the reformer reactors at turn down capacity (50%) with fresh catalyst activity, in the absence of catalyst circulation/regeneration, to generate a coke content of 4 wt%–6 wt%. However, due to unforeseen multiple issues explained above, the circulation was not started within the estimated two weeks time; whereas, the H2-rich gas production, a key indicator of catalyst activity and H2 yield, showed a 30% significant reduction from initial production, signaling escalating coke accumulation on the catalyst in the reactor section.
Eventually, the team proceeded to catalyst circulation without NHT unit startup, and efforts were focused on adjusting the pressure profiles across reactor and regeneration sections. Unfortunately, another catastrophic setback occurred during catalyst circulation commissioning, as the expansion bellow between the first upper hopper and the reduction chamber was in leak condition. FIG. 5 highlights the damage/repair of the expansion bellow.
With no spare similar expansion bellow available, the circulation was again put on hold to repair the damaged expansion bellow, during which the H2-rich gas production collapsed further to only 40% of initial production, representing the expedited deactivation of reformer catalyst at higher coke levels. In addition, the downstream compressors also struggled to maintain pressure, running at minimum rpm with spill back valves open to avoid surge conditions.
By the time the expansion bellow was rectified, the situation had reached a tipping point, despite increasing the feed rate to 70% to boost H2 production—a move that yielded only additional 4,000 Nm3/hr. With H2 production inadequate to sustain PSA and reactor pressure profiles in disarray, the imbalance persisted, and the unit was forced to shutdown. By this time, the coke levels on the reactor section catalyst has surged to around 12 wt% (analyzed by taking catalyst from the last reactor), far exceeding the regenerator’s design capacity of 7 wt% and setting the stage for unprecedented regeneration challenge.
The series of failures experienced during unit startup—including H2 supply shortage, limited heavy naphtha feedstock, equipment mechanical issues and design inaccuracies with process upsets—combined to create a serious crisis. Due to the inability of catalyst circulation and regeneration for almost three weeks, the stagnant catalyst in the reforming reactors got severely coked with fresh catalyst still residing in the regenerator section. Moreover, conditions that led to insufficient H2 production that also restricted another attempted unit restart showed how complex it can be to commission large-scale hydrocarbon processing units.
Innovative solution. Preventing the ex-situ regeneration of high coked catalyst requires hundreds of reactor section catalyst tonses to be offloaded from reactors and transffered to an offsite third-party regeneration facility. The safety concerns and the time require for this option would carry a significant financial impact.
Alternatively, to address this unique challenge of regenerating high coked catalyst without an online reforming reactors section, the Jazan refinery team worked closely with the authors’ company’s central engineering team and unit licensor Axens. Together, the team came up with an innovative solution that varied from the normal operation of reforming unit technology. A new regeneration process was developed, using nitrogen—partly relying on existing nitrogen capabilities—while supplementing it with additional temporary vaporizers, as shown in FIG. 6. The creation of this procedure with specific guidelines for this type of high coke regeneration, without prior experience, presented significant challenges and proved to be a great example of teamwork and innovation.
The innovative solution proposed using nitrogen as a temporary lift medium mimmicks H2’s role in establishing pressure gradients between reactors and the regenerator. Pressurizing the reactor section to similar operating pressures with nitrogen and linking pressure-controlled nitrogen sources to catalyst lift pots enables batch-wise catalyst circulation. Moreover, this approach required precise coordination: nitrogen flows were intermittently activated to lift catalyst batches through interstage lift lines while maintaining regenerator temperatures for controlled “black burn” regeneration with a low-oxygen environment.
Debottlenecking implementation challenges. Despite its success, the solution was not without limitations. Operating under non-design conditions presented several challenges, including catalyst flow restriction, leading to chocked lift lines. This was mitigated by optimizing the flow velocities, variation in primary lift flows and, in a worst-case, manual intervention of catalyst lift line dumping. Moreover, alongside the operating regeneration section on low oxygen-black burn mode, burning zones were carefully operated to accommodate the sudden change in coke content from high spent catalyst on the reactor side to fresh catalyst. This is especially true where fresh or very low coke catalyst will be replaced by the fourth reactor high coked catalyst batch—based on calculated cycles of catalyst shift—to handle the unprecedented coke load, preventing sudden exotherm in the regenerator. Furthermore, the existing limitation in the nitrogen system to only accommodate two lifts at one time was resolved by arranging additional nitrogen volume through external sources and vaporizers, injecting to the lift lines with regulated pressures to improve the catalyst movement for smooth continuous circulation rate and stable regeneration condition.
Solution outcomes. The results were transformative. After weeks of meticulous execution, catalyst coke content plummeted from ~12 wt% to 0.2 wt%, re-establishing H2 production capacity and enabling unit restart on January 31, 2022. During the initial catalyst batch-wise circulation cycles with black burn mode regeneration, the coke content on catalyst pills was not fully recovered from the regenerated catalyst. However, it was being reduced from the initial high coke content and was brought within the operating range for a subsequent cycle of catalyst regeneration. In FIG. 7, the right picture elaborates the transformation of high coked catalyst to fully regenerated catalyst compared with fresh catalyst, while the left picture shows the residual coke inside the catalyst pills of partially regenerated catalyst upon catalyst pill breaking.
Post two black burn mode complete cycles, the coked catalyst was fully regenerated without any exotherm, which allows the restart of the reformer reactor section, followed by white/standard burn regeneration. All other operating parameters were stabilized, validating nitrogen’s role as a temporary lift medium. Later, the unit achieved extended run despite initial constraints, demonstrating resilience under non-design conditions, whereas H2-rich gas compressors, once plagued by mechanical failures, were repaired and restarted, ensuring long-term operational stability.
Takeaways. The JZR CCR J10 regeneration case exemplifies the power of adaptive engineering and cross-functional collaboration in overcoming operational crises. By leveraging nitrogen as a temporary lift medium and pioneering batch-wise circulation followed by continuous circulation, the team not only salvaged a high-value asset but also contributed to industry knowledge on CCR unit resilience. This approach sets a precedent for similar facilities facing H2 supply disruptions, proving that innovation under constraints can yield transformative outcomes. HP
ACKNOWLEDGEMENT
The authors would like to express their gratitude to the Jazan Refinery Complex Management, Saudi Aramco, the Process and Control Systems Department Management, and the unit licensor Axens for their collaboration and support in implementing the innovative solution to address the challenges encountered under non-design conditions.
Syed Abdul Wahab Ali is a Process Engineer with the Saudi Aramco Engineering Department, specializing in refinery hydroprocessing, catalytic reforming, aromatics, utilities and H2-related units, along with specialized skills in commissioning startups, operations, processes and economic strategic planning. He is a qualified chemical engineer with more than 13 yrs of extensive experience in the oil and gas industry. Ali is an active member of several international professional organizations, including Engineers Australia and the Institution of Chemical Engineers (IChemE) in the UK. He holds multiple industry-recognized certifications, such as NEBOSH, TAPRoot, HAZOP, Six Sigma, and is an expert user of Aspen HYSYS simulation software. He earned an MBA and an MS degree in chemical engineering, reflecting his strong technical expertise. The author can be reached at syedabdulwahab.ali@aramco.com.
Abdulelah S. Ghadeer is a Process Engineer at Saudi Aramco, specializing in naphtha hydroprocessing, reforming, aromatics extraction and processing units. He is a chemical engineer with more than 11 yrs of industrial experience in refining and petrochemicals facilities. Ghadeer holds an MS degree in refining and petrochemicals from IFP School, Rueil Malmaison, France, and a BS degree in chemical engineering from King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia. The author can be reached at abdulelah.ghadeer@aramco.com
Andres Rodriguez is a Process Engineering Manager with Saudi Aramco, and brings more than 24 yrs of extensive experience in the oil and gas industry. He has specialized knowledge in various refining units, including sulfur recovery units (SRU), hydrodesulfurization (HDT), amine regeneration units (ARUs), sour water stripping (SWS), diesel hydrotreating (DHT) and gasification processes. Throughout his career, Rodriguez has worked throughout multiple countries, including France, Canada, Mexico, the United Arab Emirates and Saudi Arabia. In the past decade, he has played a key role in the design, commissioning and startup phases of the Jazan Refinery project. Rodriguez earned an MBA as well an MS degree in chemical refining, reflecting his deep technical foundation and highlighting his strategic and managerial capabilities. The author can be reached at andres.rodriguezsarmiento@aramco.com.