Saudi Aramco converts Yanbu fixed-bed reformer into CCR

Fig. 1 shows a flow diagram of the Yanbu refinery.

Fixed-bed reformer

The Yanbu reformer was originally designed as a fixed-bed unit to process 35,000 b/d of HSRN and to produce 26,250 b/d of platformate at 94 RON. In 1995, the unit throughput rate was increased to 38,000 b/d and an operating severity of 96 RONC. The unit was shutdown every 6-8 months as part of a cycle to regenerate and restore the activity of the platforming catalyst.

The reformer originally consisted of three fixed-bed reactors that used UOP platforming R-56 catalyst. The unit reheat section has one charge heater and two interheaters to maintain the required reaction temperature at each catalyst bed. In addition, four vertical combined-feed exchangers preheat the charge feed and cool the last reactor effluent product platformate.

Two recycle gas compressors recycle the required hydrogen for the platforming reactions. Additionally, three make-up gas compressors feed hydrogen to the hydrotreating units. The unit has a gas-liquid separator to separate the rich gas from the product liquid platformate.

Fig. 2 shows the reformer fixed-bed process flow diagram.

Revamp objectives

In October 2002, Saudi Aramco approved a capital project to convert the old fixed-bed reformer to a CCR unit. Foster Wheeler performed the project proposal and detailed design, procurement, and construction was awarded to Snamprogetti.

The revamp’s main objective was to increase the volume of the refinery’s unleaded gasoline pool to help meet Saudi Arabian gasoline demands and to reduce imports. The additional 95 RON gasoline production specification amounted to about 8,000 b/d and the annual revenue will be in the millions.

The additional production reduces the requirement for expensive purchased blending components such as MTBE and allows for blending of higher volumes of LSRN, butane, and other lower-cost components into the gasoline pool. The revamp also increases the unit service factor because downtime for regenerations will be eliminated.

The revamped unit performs the same function—reforming heavy naphtha to high-octane reformate. The revamped CCR reformer produces 100 RON platformate at 75.5% C5+ yield, 230.3 cu m hydrogen/cu m of feed, and at a 40,000 b/d charge rate. The old fixed-bed reformer production was 96 RON at 76% yield and 38,000 b/d maximum charge rate.

Continuous catalyst regeneration maintains RON, yield, and charge rate capability without the need for regeneration downtime.

Revamp strategy

After completing all construction and precommissioning activities, Saudi Aramco planned to shut down the old fixed-bed unit to perform the required modifications to change the unit configuration to CCR. Also during the shutdown, regeneration of the old catalyst was completed before starting the mechanical activities. Regeneration of the old catalyst was done to prepare the catalyst for dumping, screening, and platinum recovery.

The regeneration included only the carbon burn step without chloride injection, which saved about $12,000. The regeneration was completed successfully and the carbon level after carbon burn was 0.35 wt %.

After completing the regeneration, the old fixed catalyst R-56 was unloaded and screened for metal recovery. Then the old three reactors were demolished. About 256 mechanical tie-ins were completed during this shutdown, which took 28 days to complete.

Revamped reformer

The Yanbu fixed-bed reformer unit was revamped to CCR on June 2006. The major changes for this conversion were:

• Reforming stacked reactors. The old series reforming fixed-bed reactors were replaced with three new reforming stacked reactors. The important feature of the stacked reactors is the low pressure drop to facilitate the catalyst movement from the reactor to the regenerator. The design pressure drop is 0.24, 0.23, and 0.31 kg/sq cm for Reactors 1, 2, and 3, respectively.
• Cycle max CCR. The revamp incorporated a new UOP CCR cycle max model, which was the first unit of its type for Saudi Aramco. The CCR is designed to regenerate continuously the Platforming UOP-R234 catalyst at 100 % circulation rate or 2,000 lb/hr (907 kg/hr) to maintain the catalyst selectivity and activity.
• New CCR refrigeration unit. A new CCR refrigeration package was installed as part of the revamp. The objective of this unit is to increase the purity feeding the CCR reduction zone, lock hopper, and the regenerated catalyst lift line.
• New waste-heat boiler. As part of the revamp and to optimize the refinery energy savings, a new waste-heat boiler (WHB) was installed in the main duct of the reformer heaters. The WHB uses waste energy from the reformer heater flue gas to generate 150-psi steam at a design rate of 35 tons/hr with future spare capacity to produce 60 tons/hr.
• Platformer heater modifications. Saudi Aramco modified the reformer heaters to maintain the required heat duty to perform the platforming endothermic reactions. The existing second and third interheaters were combined and converted into one interheater to maintain inlet temperature to the second stacked reactor. In addition, a new heater was designed to maintain the reaction inlet temperature of the last reformer’s stacked reactor. The revamped reformer unit has four total heaters including the charge heater.
• Net gas system modification. In a modification of the net gas system as part of the revamp, the old makeup gas compressors were reused to supply hydrogen to the CCR unit. Two new compressors were installed to supply the refinery hydrotreating’s isomerization units with the required hydrogen.
• AET LPG recovery unit. A new Advanced Extraction Technology unit was designed as part of the overall revamp. The objective of this unit is to maximize LPG recovery from the reformer’s net gas stream and increase the hydrogen purity of the net gas to meet the required hydrogen purity for the new diesel hydrotreater. The AET unit is designed to recover 98% LPG and increase the purity of the net gas to 89 mole % from 80 mole %.
• Net gas chloride treaters. Two new chloride treaters were installed on the makeup gas to the refinery’s hydrotreating units and the net gas feeding the new diesel hydrotreater. These chloride treaters maintain a low chloride level (1.0 ppm maximum) in the effluent hydrogen gas to guard the downstream unit users from corrosion-related problems.

Fig. 3 shows the revamped Yanbu reformer reactor system. Fig. 4 shows the new CCR interaction with the reactor system.

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Performance comparison

Table 1 shows a performance comparison between the reformer before revamp and after conversion to a CCR unit.

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Lessons learned

During the revamp, we experienced several obstacles, but preparedness and teamwork effectively minimized their effect on the project. Here are the major lessons learned from the experiences of this revamp project:

• Implement a team approach and culture for other projects. Project stakeholders included project managment team, Yanbu refinery, contractors, loss-prevention employees, inspectors, and other parties. Traditionally, the various stakeholders had different interests, lack of common objectives, lack of transparency, and inadequate planning and communication. This often led to project delays. Saudi Aramco initiated the team concept for this project, integrating all stakeholders into one overall team.
  
  Benefits of the team concept included reduced project costs because everybody worked for the same company; shared and achieved common objectives; prepared planning and coordination for common activities such as the distributed control system, instrumentation, electrical, etc.; and it created a positive environment for operations.
• Use an automated mechanical completion acceptance system to manage exception items and mechanical completion certificate approvals. Previous projects used a conventional manual hardcopy report system for tracking exception items. Yanbu projects have successfully used an automated system automatically to log, track, and close exception items.
  
  The automated system helped us expedite exception item handling through an easy-to-use system, improve transparency, achieve project accountability, support focusing on project completion and closure, better track exception items, generate many variety of useful reports, reduce documentation, and save time.
• Ensure consistencies in vendor data. During commissioning, we observed that one of the equipment nameplate recommend using an oil-type material while the equipment document and manual referred to different material types. The team contacted the vendor, which confirmed that the manual was correct. Equipment nameplate and manuals should match each other.
• Consider inspecting equipment. One of the vessels failed during start-up. The investigation revealed that there was no requirement governing the internal inspection of vessels. We learned that the vendor and plant owner should inspect vessel interiors to avoid unexpected problems.

Based on an article that appeared in the Saudi Aramco Journal of Technology, Fall 2007, p. 49.

The authors

Mohammed A. Balamesh ([email protected]) is a process engineer working at Saudi Aramco’s process and control system department, Dhahran. He joined Saudi Aramco in November 1990. Balamesh has 9 years of refining experience, working in Saudi Aramco refineries in Jiddah, Ras Tanura, and Yanbu. He also has 5 years’ experience working with process engineering in Dhahran. Balamesh holds a BS from King Abdul Aziz University, Jiddah, and an MS from the University of Tulsa, both in chemical engineering.

Rabea M. Al-Saggaf is a process engineer at Saudi Aramco, Yanbu. He joined Saudi Aramco in 1996 and has 10 years of refining experience. He holds a BS in chemical engineering (1996) from King Abdul Aziz University, Jiddah.