Unique Sardinian refinery focuses on third-party crude processing

Saras refinery at Sarroch, Sardinia, is unique in its combination of operational scope, size, and strategic location as a refinery that specializes in third-party processing. Photo courtesy Saras SpA Raffinerie Sarde.

For years, the 285,000 b/cd (15 million metric ton/year) refinery has employed a strategic location, abundant storage, and advanced processing capability to refine crude oil for other refiners and oil producers. In recent years, about 60-90% of all processing at the refinery has been for third parties.

Although the company refines crude for its own account as well, providing process capacity for others is the company's core business, says Giuseppe Citterio, Saras' manager of strategic planning. There are other refineries with capacity for hire, but none with the combination of operational scope, size, and strategic location of Saras.

Typical service arrangements, which can be complex, are covered by long or medium-term (about 1 year) contracts. Such service is also provided on a short-term basis, even a spot basis.

Saras will in some cases purchase products, exchange them, or supply products different from those the contracted crude would yield. The contracts can even be written to select the operating mode of the process employed-cracking, visbreaking, catalytic reforming, desulfurization, or a combination of them.

Because most Saras clients supply their own crudes, the refinery must cope with a myriad of crudes-25 in a typical year and a total of 40 the past 5 years.

In addition, the company must, to keep its configuration up to date, pay close attention to diverse, evolving product markets in North Africa, the Near East, Europe and North and South America. Specifications in these regions range from those that permit primitive gasolines with heavy doses of lead anti-knock compounds to those that require ultra-low sulfur diesel and unleaded, reformulated fuels.

A case in point was the introduction of reformulated gasoline in the U.S. This prompted the company to seriously consider installing a methyl tertiary butyl ether unit at the Sarroch site. That has been dropped, however, to concentrate on another case in point: the deteriorating world and Italian market for high-sulfur, high-metals residual fuel oil and coke.

Saras' response to this was to set up a joint venture with Enron Corp., Houston, to build an integrated gasification combined-cycle (IGCC) plant on the refinery site. The joint venture project will use an undesirable refinery stream to generate about 40% of Sardinia's electricity needs.

Feedstock for the unit will be a heavy tar that will be converted into hydrogen and electricity. This project is described in more detail in an accompanying article on p. 33.

Products

Saras has already cleared one hurdle in responding to the large variations in its clients' requests and in filling its own export needs.

It made major investments to meet Europe's tough, 0.05 wt % sulfur level in diesel. This entailed the addition of a new hydrogen network, including two pressure-swing adsorption units and extensive improvements to its hydrotreaters.

The company's clients also want jet fuel produced to international specifications, minor volumes of European-spec (0.2% sulfur) heating oil, and high-sulfur gas oil for South America and the Far East.

Gasolines include European grades of unleaded at 95 and 98 RON and leaded at 97 RON (0.56 g/gal).

Saras also produces leaded gasolines for various markets in Lebanon, Turkey, and West Africa that have as much as 1.5 g/gal lead content.

The company also makes various unleaded and low-aromatics blend stocks.

The company

The late Italian industrialist Angelo Moratti recognized the strategic importance of refineries in the Mediterranean.

He built the Saras refinery, which went on stream in 1965. Moratti, also a shipbuilder, previously had built and operated a toll refinery at Agusta, Sicily. He sold this to an Exxon Corp. affiliate before launching the Sardinian project at Sarroch, south of the island capital of Cagliari.

This location, just several hundred miles across the Mediterranean from Tunisia, was at that time a rustic region with dirt roads and marginal infrastructure. Since then tourists have made it one of Europe's most attractive travel destinations.

Saras is still a family-owned company, with Gian Marco Moratti chairman and Massino Moratti managing director.

The Italian state company Agip Petroli holds a 15% share in Saras. Agip has a representative on the board and a dispatching group in the refinery for delivery activity. But it is not involved in Saras strategic planning or operations.

Saras is also active in the commercial market in Italy for LPG, gas oil, and fuel oil through its wholly owned subsidiary, Arcola Petrolifera SpA at La Spezia, south of Genoa. There is a small refinery with only topping capability at La Spezia, but the terminal there has a storage capacity of nearly 1.6 million bbl. It supplies products to the Italian mainland.

In Spain, Saras has a 50-50 retail gasoline and diesel venture with a European affiliate of Conoco Inc. that markets under Conoco's Jet brand. A construction program aims at a total of 200 modern service stations by 2000. Also in Spain, Saras has a majority interest in Saroil SA, which distributes gasoline, diesel, and heating oil from the Saras refinery.

Saras says the Spanish strategy will enable Saras to become fully integrated downstream for that part of its capacity not committed to third party processing.

Tanker traffic

All crude for the refinery comes in by tanker. Most of the products leave that way.

Tankers calling at the refinery tie up either at a jetty extending 1.6 km into the Mediterranean or at a platform in deeper water.

The 10 berths of the jetty, which is about 10 miles south of the port of Cagliari, can take ships with drafts of 20-39.6 ft.

The two berths at the platform can handle ships needing 57-68 ft of water. This means tankers of 160,000 to 260,000 dwt. This platform is connected by two overwater 42-in. lines-one heated for waxy crudes-on pilings.

Two kinds of crude tankers make up most of the Mediterranean traffic. The ones from North Africa and the former Soviet Union (FSU) carry about 500,000-600,000 bbl of crude. Larger ones from the Middle East and the North Sea come with cargoes of about 1 million bbl. Tankers can be unloaded at the island berths at a rate of about 70,000 bbl/hr.

FSU crude, still known by its old designation, Soviet export blend, is shipped from Novorossiisk through the Black Sea to the Mediterranean.

Middle East crude comes directly from the Persian Gulf or via the Red Sea to the Gulf of Suez, where it is off- loaded into the Sumed pipeline and sent to the port of Alexandria on the Mediterranean. Other crudes come from North African ports.

Iraqi crude, formerly shipped from Ceyhan, Turkey, was processed by Saras before sanctions against Iraqi oil exports went into effect. Should that crude enter the market again, the pipeline across Turkey would require major maintenance before it can resume its role as an outlet for Iraqi oil exports.

In addition to FSU crude blends of differing qualities and North Sea Brent, Saras has refined from time to time all North African and Nigerian crudes and most of those from the Persian Gulf, including Arabian and Iranian heavy crudes. More than 10 atmospheric residues of differing quality are also upgraded.

In summary, the refinery slate includes sour crudes and resids primarily from the Middle East and FSU; waxy paraffinic crude, mainly Libyan; and sweet crudes and resids from a variety of sources, even as far away as Indonesia.

Storage

Storage volume and flexibility are critical to the type of refining that Saras practices, particularly when total capacity is 285,000 b/cd.

The refinery has a total storage capacity (crude, products and gases) of 4.5 million cu m. Of this, there are 19 crude tanks with a capacity of 1.06 million cu m. The largest of these has a capacity of 160,000 cu m.

In the products area, 57 tanks are dedicated to black products, 58 to white, and 36 to gases.

Four tanks are being removed to make space for the IGCC plant while a replacement tank is being added.

Refinery configuration

The simplified flow diagram and accompanying table of unit capacities on p. 17 give an overview of the capabilities of the Sarroch refinery.

Some details on the units follow:

• Distillation. Topping unit No. 1 is partially employed in distillation of waxy crude, while unit RT2 is used at times in resid distillation (the RT signifies the unit was revamped). Topping unit No. 2 is fully integrated with wet vacuum unit No. 2.

• Visbreaking. The visbreaker employs the Shell soaker design. It began life in 1973 as a topping unit that was modified in 1983 to visbreaking and further modified to the Shell design in 1990. In Italy, refineries have legal capacities and operating capacities. Saras' operating capacity is 15 million tons/year, but its legal capacity is 18 million tons/year. It can reach this level by converting the visbreaker back to a distillation unit.

• Mild hydrocracking. This unit, completed in 1992, is one of the newest major units at the refinery and is expected to have an important role for years. Saras has taken steps to enable it to eventually double capacity of the unit to 100,000 b/d by adding a second train. It earlier installed a first train, consisting of two reactors and a fractionator. The design and initial investment permit a configuration of two trains, each with three reactors, using a common fractionator. Citerrio says the rationale for this is to increase hydrotreating capacity to improve the quality of gas oil to meet European specifications in 2000. The unit can handle vacuum or atmospheric gas oil or mixtures. It operates at 100 bar (1,429 psi) pressure and uses conventional NiMo plus CoMo catalysts. Sometimes a zeolitic catalyst is used in the last bed. About 20-30% of the total throughput is cracked.

• Fluid catalytic cracker. The UOP FCC unit has been extensively revamped during each turnaround. It has a vented riser and employs partial combustion regeneration. The unit includes a 120-ton/hr CO boiler and a 16,000-kw expander.

• Alkylation. The HF alkylation unit is licensed from Phillips Petroleum Co. Its safety system includes a spray water system, split reaction loop, and fast acid recovery.

• Catalytic reformer. This is a UOP continuous catalytic reformer (CCR) unit with a naphtha hydrotreater. It produces 100 RON clear reformate from a naphtha top cut. This unit is not large enough to supply the refinery needs, so Saras sends naphtha to the nearby Enichem SpA petrochemical complex, which returns reformate to Saras.

• Hydrotreaters. The refinery has 75,000 b/d of distillate hydrotreating capacity in four units. The two gas oil hydrotreaters use high-purity hydrogen and can knock down sulfur content to 0.05%. The other two units are mainly used for the hydrotreating kerosine. Hydrogen from catalytic reforming that is used for hydrotreating and cracking is purified to 99.5% in two pressure-swing adsorption units. It is essential to have this level of purity to make the 0.05% sulfur specification for the gasoline. This desulfurization and mild hydrocracking require three sulfur recovery plants. An old unit built in 1975 is rated at 90 tons/day. Two additional, 200 ton/day units were added with the hydrocracker in 1992-93.

• Desalination. With the growth of tourism in Sardinia, water is in tight supply there, particularly in the summer. As a result, Saras 3 years ago built a seawater desalination plant that produces a maximum 320 cu m/hr (85,000 gal/hr) of water. It is used in processing units and as boiler-feed water. The refinery operates a stringent water conservation program, emphasizing air cooling and recycling of treated waste water. A result is that the refinery uses water at a rate of less than 0.4 cu m/ton (14 gal/bbl) of crude processed.

• Power equipment. Most of the refinery's power is generated onsite by a thermoelectric power station. The station has three boilers that generate 300 ton/hr steam at 72 atm (1,059 psi). Three turbines power generators (two 11,200 kw and one 16,000 kw) and provide process steam. An expander on the FCC unit furnishes an additional 14,000 kw of power. In the future, most of the refinery power will come from the IGCC plant. Refinery utilities are also integrated with the adjacent Enichem petrochemical complex.

The environment

Because Sardinia has become one of Europe's more popular tourist destinations, Saras must remain especially vigilant and sensitive to environmental matters.

The company guarantees compliance with water discharge standards. The refinery also provides full-scale treatment for ballast water, which is no small amount, with 25 million tons of crude oil and products coming and going though its shipping facilities.

The current limits, in mg/l., on water released are: chemical oxygen demand, 160; ammonium ion, 15; and hydrocarbon oil, 5. Maximum temperature allowed is 35° C (95° F).

The air quality surrounding the refinery is continuously monitored by an analyzer network that measures sulfur dioxide and dust and transmits the values directly to the refinery and local authorities.

Beginning Jan. 1, 1998, the emission limits in mg/cu m-as an average value of all stack emissions-will be SOx 1700, NOx 500, dust 80, and CO 250.

Addition of the IGCC plant will slightly improve overall site emissions. This plant, characterized by its low emissions, will export electricity and steam to the refinery, allowing the refinery to reduce the amount of fuel it now burns, meaning fewer emissions.

Copyright 1996 Oil & Gas Journal. All Rights Reserved.