LYONDELL, CITGO JOIN FOP HEAVY OIL UPGRADE PROJECT AT HOUSTON REFINERY

Anne K. Rhodes
Refining/Petrochemical
Editor

Lyondell-Citgo Refining Co. Ltd. is beginning an $800-million upgrade and expansion of its Houston refinery. The project will enable the refinery to produce clean fuels while processing about 80% heavy, high-sulfur Venezuelan crude oil.

Lyondell Petrochemical Co. and Citgo Petroleum Corp., a subsidiary of Venezuela's state-owned company Petroleos de Venezuela S.A., formed the venture to conduct a major upgrade, provide a long-term crude supply for Lyondell-Citgo, and provide a long-term product supply, for Citgo. Start-up of the new facilities is scheduled for year-end 1996.

HOUSTON REFINERY

The 265,000 b/d refinery is a full-conversion plant with facilities for fluid catalytic cracking (FCC), coking, catalytic reforming, sulfur recovery, and hydrotreating. Lyondell Petrochemical contributed these assets to the venture, while Citgo contributed most of the capital to fund the expansion.

Lyondell-Citgo is currently owned 90% by Lyondell and 10% by Citgo. When the heavy-oils project comes on stream, however Citgo's share will increase to about 35%. Citgo can increase its share to 50% after the expansion, and has expressed its intention to do so, said William E. Haynes, president and chief executive officer of Lyondell-Citgo.

Lyondell-Citgo comprises three business units: refined products, lubricating oils, and aromatics. In addition to transportation fuels, the refinery produces:

Lubricating base and finished stocks for use in naphthenic and paraffinic industrial and automotive lubes
Benzene, toluene, and para and ortho-xylene
Food-grade oils and other specially products.

Citgo is marketing most refined products from the refinery (gasoline, diesel, and jet/kerosine) in the U.S. The refinery's heavy crude supply contract is with Lagoven S.A., a subsidiary of Petroleos de Venezuela. Since its July 1993 start, the venture co already seen increased profits from the processing of heavy oil, said Haynes.

The refinery processes about 40,000 b/d of West Texas Intermediate (WTI) or equivalent crude, which is used to produce the lube oil cuts. About 130,000 b/d of 22 API Venezuelan crude, called BCF22, is also processed.

After the expansion, 200,000 b/d of BCF17-a 17 API Venezuelan crude - will be processed.

Because the refinery produces aromatics and is integrated with Lyondell Petrochemical's Channelview, Tex., ethylene plants, which also produce gasoline components, it is in a good position to produce reformulated fuels. Benzene is extracted from the refinery's gasoline stream, so the company is already producing gasoline containing less than 1 vol % benzene. In fact, this past winter, the plant produced about 25,000 b/d of oxygenated gasoline, said Haynes.

The expansion project is expected to enable Lyondell-Citgo to oxygenated about 750(, of its gasoline and produce 100% low-sulfur diesel.

EXPANSION PROJECT

The Houston refinery operates three crude distillation units:

A 6,000 b/d still for processing naphthenic crudes (The front-end and resid from this unit go to fuels production.)
A 40,000 b/d still for processing paraffinic crudes for lubes production
An 80,000 b/d still for intermediate-quality crude (This unit produces low-sulfur resid.)
A 140,000 b/d still which processes BCF22 and fills the coker.

The intermediate still will be replaced with a new crude unit, resembling the existing 140,000 b/d unit.

The accompanying flow diagram of the refinery indicates existing units, units slated fo revamp, and units to be added. The major additions include:

A 100,000 b/d crude distillation unit, including a vacuum tower and desalter.
A 45,000 b/d low-pressure, low-recycle, delayed coker to produce about 2,800 tons/day of shot coke.
A 45,000 b/d gas oil hydrotreater to desulfurize and denitrogenate additional FCC feed.
A 235 long tons/day sulfur-recovery plant.

John Years, vice-president, manufacturing for Lyondell-Citgo, says these units will create essentially a second, parallel processing train at the refinery.

The catalytic cracker feed hydrotreating process reduces FCC sulfur emissions, improves unit conversion, and reduces gasoline sulfur content.

Although the refinery, currently hydrotreats about 75% of its FCC feed, the additional hydroprocessing capacity will aid efforts to produce about 100,000 b/d of low-sulfur diesel fuel. (The plant now produces about 70,000 b/d of higher-sulfur diesel.)

The Houston refinery typically operates two reformers: A benzene/toluene reformer and a "Magnaformer," or high-end-point reformer that produces xylenes. A third unit is brought on fine when the other two are down, or when low-cost reformer feed is available.

Because these reformers produce a lot of hydrogen, and because the refinery is integrated with Lyondell's petrochemical plant across the Houston ship channel, no major hydrogen deficit is expected.

Currently, incremental, or "trim," hydrogen needs are supplied by Air Products & Chemicals Inc's Gulf Coast hydrogen pipeline. Additional hydrogen supply from a third party will be required after the expansion, according to Years.

No modifications to shipping or storage facilities will be required to import the new crude. Transportation within the refinery is facilitated by the company's practice of keeping inventories at minimum levels, said Yoars.

TECHNOLOGIES

The new units will utilize common industry technologies:

Hydrotreating - UOP, Des Plaines, III.
Coking - Foster Wheeler, Clinton, N.J.
Crude distillation - KBC Advanced Technologies Ltd., Weybridge, England.
Sulfur recovery - Pritchard Corp., Overland Park, Kan.

The sulfur plant will include amine contacting sour water stripping, and the potential for oxygen enrichment.

OPERATIONAL CHANGES

One of the project's primary goals is to fully convert 17 API crude without dependence on outside sources for feedstocks to dilute the negative effects of processing the crude, sails Lavergne.

Venezuelan BCF17 crude is high in ring-structure species and nitrogen. The crude is also high in metals especially vanadium-and has poor diesel quality in terms of gravity and cetane index.

The increased nitrogen content will produce additional ammonia in the wash water, says Lavergne. The combustion chambers in the new Claus units, however, will help mitigate the problem.

BCF17 is also high in naphthenic acid content, which can cause corrosion (OGJ, Feb. 28, p. 31). Metallurgy in parts of the existing still will be upgraded to 317L stainless steel cladding, according to Lavergne. The new crude unit also will contain appropriate corrosion-resistant metallurgy.

The incremental resid production will be pumped off of the still, to unload the column. In addition, according to Lavergne, the tower will be operated in "deep-cut" mode, which will produce more gas oil and less lower-value resid.

The refinery's integration with Lyondell's Channelview petrochemical plant gives it flexibility in its processing options. It now sends about 15-20,000 b/d of low-octane paraffins to Channelview for use as steam cracker feedstock. It also receives streams, including feedstocks for the benzene/toluene reformer and pyrolysis gasoline, from the Channelview plant.

The refinery purchases about 20,000 b/d of gas oil as FCC feed. After the expansion, however, it will no longer need to exercise this option, salts Years.

The upgrade will cause little change in the refinery's light products slate. Gasoline production will remain about the same, kerosine production will decrease slightly, and diesel output will increase slightly.

Likewise, very little low-sulfur resid will be produced. But because the heavier crude slate will produce more bottoms, coke production will essentially, double.

As marketer of the refinery's products, Citgo will market the additional coke. The refinery, however, is looking to cogeneration facilities as a possible market for the coke.

(Lyondell-Citgo is involved in a cogeneration project, separate from the expansion, with AES Deepwater Inc. The refinery, sends about half of its coke production to AES, who, iii turn, supplies the refinery with additional steam.)

Where the existing coker is drilled to a railcar, the new coker will be drilled to a pit. Coker gas oil production also will increase.

Two new cooling towers will be required for the expansion: one as part of the coker and one as part of the sulfur plant.

The cooling tower for the existing 80,000 b/d crude unit will be large enough to cover the new, larger still that will replace it.

The refinery imports methyl tertiary butyl ether (MTBE) from Lyondell Petrochemical's Channelview facility. Lyondell-Citgo plans to oxygenate about 75% of its gasoline after the revamp, says Years.

As a testament to the deep-cut conversion capability of the revamped refinery, its gasoline and diesel production will be about 75% on crude, about the same as it is today.

OTHER PROJECTS

Several projects not directly related to the heavy oil upgrade are under way:

The preheat section of the largest crude still was improved to increase its feed capacity.
Three of the six existing hydrotreaters will be revamped to a small degree. Of these, the only significant revamp is the upgrade of the distillate (diesel) hydrotreater, which win be modified to reduce sulfur and meet cetane and gravity specifications.
Tank mixing systems are being up graded.
The existing coker has been optimized.
A reformulated fuel blending experiment will be finished this fail.
Revamps to existing crude and hydrotreating units are being fitted into the plant's turnaround schedule, says Years.

The refinery has essentially all of the utilities it will need to operate the new units. Electric motor usage will be optimized and no new boilers or steam-production facilities win be needed. (Incidentally, the refinery, at one time, ran more than 300,000 b/d of crude, indicating that surplus utilities are available.) Two examples of how the steam balance will be affected are:

The heavier crude will produce less light-ends, which win enable the refinery to reduce steam usage in gas-plant separation columns.
The heat balance on the FCCU will require the removal of high-level heat from the FCC hydrotreater gas oil product by generating high-pressure steam.

ENVIRONMENT

Lyondell-Citgo has filed environmental permit applications and anticipates receiving the permits in mid-1994. These permits have some general provisions in common: for example, continuous emissions monitoring. But each permit also "AH have provisions specific to that unit. Until the permitting phase is complete, these specifics will not be known precisely.

To facilitate the permitting process, the refinery is communicating face-to-face with Texas authorities whenever possible (rather than through the mails), says environment manager Janice Hiroms.

The project is covered by the U.S. Environmental Protection Agency's prevention of significant deterioration (PSD) regulations. The PSD regulation is concerned with net changes in emissions of five criteria pollutants. Because the heavy-oils upgrade project has not exceeded those levels, no PSD-type permits will be required. This is called, "netting out," says Faheem Kazimi, health, safety, and environment supervisor, expansion project.

EMISSIONS

Lyondell-Citgo is designing the expansion with existing and anticipated environmental requirements in mind. Best available control technology-including such items as enclosed relief valves and low-NO, burners - will be employed for all new and modified units, says Hiroms. The specialized burners will be used on all fired units, ne,A, and revamped.

All waste waters will be segregated and handled according to four classifications, says Kazimi: Benzene Neshap, oily water, contaminated storm water, and uncontaminated storm water.

All of the equipment associated with the new units will be tied to a closed flare-header system, thus eliminating atmospheric emissions. Also included in the project will be analyzers on all of the stack heaters, as required.

All of the waste water from the new units will be hard-piped and pumped to the water treatment area. A few streams will have to be separated and sent to the existing benzene stripper to comply with national emissions standards for hazardous air pollutants (Neshap), said Lavergne.

The sulfur plant will be built with 75% redundant capacity, according to Hiroms. The company is upgrading the existing sulfur plant to the same specifications.

Among other sulfur-plant controls will be instrumentation to control the Claus beds and ensure the proper H2S-to-SO2 ratio.

The refinery has a waste minimization team that looks for opportunities to eliminate, minimize, or recycle wastes. Included in this effort is the effort to recycle as much water as possible within the refinery. For example, coke-bed water is filtered, then recycled to quenching.

The team is looking for similar opportunities for solid wastes, says Hiroms.

Lyondell-Citgo is evaluating reprocessing sludges in the coker. The company also is continuing to expand its program for collecting and reprocessing used automotive lubricants (OGJ, Feb. 17, 1992, p. 27).

The refinery has an internal program for monitoring fugitive emissions, says Hiroms, that exceeds federal and state requirements. Using a 500 ppm leak-detection limit, all benzene point sources are tested for leaks monthly. Leaking components must be repaired within 15 days or placed on a shutdown fist.

Sources of volatile organic compounds are checked quarterly. Although a 10,000 ppm limit is allowed, the refinery is instituting a new program with a 500 ppm detection limit.

EXISTING PROJECTS

Several environmental projects, not directly related to the upgrade, are under way at the refinery:

Compliance with the benzene Neshap regulation was completed on schedule.
Installation of systems for recovering vapors from duck-loading facilities are under way.
A wet-gas scrubber is being installed on the FCCU during a scheduled turnaround, and will be complete in late 1994.

CONSTRUCTION

The company has completed the conceptual engineering phase of the upgrade and signed the technology agreements, and is well into the engineering and procurement stage.

The process design phase will be finished in about I month. Then afl of the project will be in the detail-engineering phase.

A materials-management program is being instituted to maintain the construction schedule, protect the materials from damage and theft, and reduce costs.

The first major construction-revamp of the existing crude unit-is scheduled to begin in October. The remaining revamps will be completed later in 1995, says Youel Baaba, vice-president and project director of the refinery expansion project.

The majority of the construction on the revamp unit will be finished at the end of first quarter 1995. Labor requirements will peak at about 3,000 during construction, says Baaba.

Safety goals for the construction are: