U.S. REFINERS MOVE INTO ANOTHER CHALLENGING TECHNICAL ERA

John R. Hall
Ashland Oil Inc.
Ashland, Ky.

With the transition to unleaded gasoline scarcely behind us, another new era is dawning for the U.S. refiner. No one yet knows the exact configuration of the refinery of the future and no two refineries are likely to adapt in exactly the same way.

What is certain, however, is that by the year 2000, refineries will be more technologically advanced, their products will be more environmentally acceptable, and their operators will be more highly trained.

The typical U.S. refinery in the year 2000 will be much the same, yet very different from the typical refinery of today.

It will be located at an existing refinery site because economic and environmental considerations will make it impossible to build new grassroots capacity.

A brand new U.S. refinery will be both economically impractical and environmentally unfeasible.

As a result of the Clean Air Act, the refinery of tomorrow will produce cleaner fuels. The entire U.S. gasoline pool will likely be reformulated. Most of the diesel fuel pool will consist of ultralow-sulfur product.

And jet fuel-which is experiencing rapid demand growth-will be an increasingly important product.

Many existing refining processes will remain in use, but they will be more efficient and more technologically advanced.

New processes will be developed to produce more oxygenates and to upgrade the bottom of the barrel, as refiners strive to comply with the Clean Air Act while coping with a heavier, higher-sulfur crude oil slate.

Energy efficiency will be a primary concern, as refiners seek to combat ever-increasing crude oil costs and refinery operating expenses.

The refinery of the future also will be much more environmentally acceptable. Emissions to air and water will be significantly reduced, and efforts will be made to eliminate solid wastes.

Sophisticated computer control systems will be used throughout the refinery to instantly and continuously optimize yields and protect the environment.

Refinery personnel will be more highly trained, reflecting the increasingly complex nature of their jobs.

These changes mean that the refining business will be even more capital-intensive tomorrow that it is today. For example, Ashland has estimated that the industry will need to invest at least $42 billion by the year 2000 just to comply with Clean Air Act regulations (Table 1).

The following is a closer look at the refinery of the future.

CLEAN FUELS

By the year 2000, it is likely that 100% of the U.S. gasoline pool will be reformulated. Although only the nine worst U.S. ozone nonattainment areas will be required to have reformulated gasoline by 1995 to combat air pollution, the Clean Air Act allows other nonattainment areas to opt into the program.

Ashland has projected that if all 96 ozone nonattainment areas opt in, 80% of the U.S. gasoline pool will have to be reformulated (Table 2).

When demand for reformulated gasoline becomes high enough, the total pool may be reformulated due to the prohibitive cost involved in maintaining three grades of both reformulated and conventional gasoline. There will of course be a major cost associated with this new gasoline (Table 2).

While the Clean Air Act has set certain standards for reformulated gasoline, it is difficult to forecast its exact composition in the year 2000 until the U.S. Environmental Protection Agency finalizes the complex model called for by the recent regulatory negotiation process between industry, government, and other parties.

However, it is expected that gasoline will be required to have oxygen content of at least 2%, lower aromatics and benzene content, a probable reduction in sulfur content, and some reduction in the 90% distillation temperature (T90).

Reformulated gasoline is likely to be available in three grades-regular, mid-grade, and premium-with about the same octane numbers as today.

Methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME) will be the dominant sources of oxygen for reformulated gasoline (Table 3).

TAME is becoming more attractive, as many refiners have already announced plans for new units. Refiners who do not have sufficient feedstock to run MTBE units at full capacity could decide to coproduce TAME. These factors will likely make TAME increasingly attractive.

Although ethanol will remain a factor, its higher cost and handling difficulties will make it less attractive than MTBE.

Refiners also may have to purchase MTBE from standalone plants, as refinery feedstocks of isobutylene and amylenes may be insufficient to meet oxygenate demand.

However, toward the end of the century, new technology-either modified FCC catalysts or improved isomerization techniques-will permit refiners to produce more of their own MTBE.

Environmental pressures to convert marine, rail, and off-highway diesel to ultralow-sulfur product will probably result in a diesel-fuel pool that is primarily ultralow-sulfur. In fact, it is likely that the use of higher-sulfur distillate for home heating oil will even be curtailed.

REFINERY PROCESSES

The refinery of the future will use new and existing units-most of which will be computer controlled-to process a broader array of crude oils, including greater volumes of heavier, higher-sulfur crude.

Fluid catalytic cracking will continue to be the workhorse of the refinery in the future. Units will be much more flexible, with the ability to handle a wide range of feedstocks. Units will have large regenerators and catalyst coolers, very short-contact riser cracking, and quick, efficient catalyst separation.

Catalysts will be much more temperature-stable, and product distribution will favor more wet gas, less dry gas, and less gasoline and slurry. The increased FCC unit wet gas will be used to produce oxygenates for the reformulated gasoline pool.

Computer models will be further developed and refined to alter reactor conditions-primarily temperature-to continuously optimize product yields.

Catalyst disposal from many refineries will be minimized by systems, such as magnetic separation, that recover metals and recycle catalyst. Catalysts will be restored at many refineries in on-site units with activated catalysts recycled to the units.

Many existing processes will continue to be used, such as catalytic reforming, alkylation, hydrotreating, and hydrocracking. But these processes will be more technologically advanced. For example, new technology is evolving for better methods to process residual fuel in both catalytic cracking and hydrocracking units.

Hydrotreating will be greatly increased in the future. Significant increases in hydrogen production to support hydrotreating will come from very-low pressure continuous catalyst regeneration reformers and the partial oxidation of very heavy bottoms.

In addition to MTBE from isobutylene and TAME from amylenes, new processes will concentrate on producing oxygenates, such as the conversion of propylene to oxygenates. New technology may be developed to permit FCC unit C4-Olefin production to be isomerized and reacted with methanol to make MTBE.

Much of the amylenes currently contained in gasoline will be used to make TAME. While some propylene may be used to make other oxygenates, the majority will continue to be alkylated.

Technology may also be developed that allows alkylation units to use a solid-acid catalyst so that they may be no longer dependent on hydrofluoric or sulfuric acids.

ENERGY UTILIZATION

The cost of electricity is expected to increase rapidly throughout this decade as utilities comply with Clean Air Act requirements. At the same time, refiners will need to use cleaner fuels in process heaters.

Consequently, energy efficiency will be a major force for change as refiners seek to control operating expenses and minimize wastes. Such energy recovery systems as power recovery turbines, cogeneration, more-efficient heat exchangers, and highly efficient burners will be increasingly important.

Computerized controls will be used to continuously maximize thermal efficiencies. Yet even with these improvements, refiners must strive to develop even more advanced technologies to further improve overall energy efficiency.

ENVIRONMENTAL COMPLIANCE

Refineries will continue to be heavily regulated and will spend a large portion of their capital budgets on pollution-control equipment,

Process heaters will be required to burn low-sulfur gases or use scrubbers and other devices to minimize emissions of particulates, sulfur dioxide, carbon monoxide, and nitrogen oxides.

Tanks will be required to have bottom liners and double seals on their roofs to minimize fugitive emissions of volatile organic compounds. In addition, all valves and seals will be designed for low or no emissions and will be constantly monitored for leaks, Sewers will be closed, and most hydrocarbon in waste water will be recovered.

Efforts will be made to eliminate solid hazardous wastes. Most water used in refinery processing will be recycled and reused. What little effluent water is discharged will be treated to meet limits that will generally make it of higher quality than influent water, and it will be nontoxic to aquatic life.

Groundwater will be monitored continuously to ensure that no contamination occurs. Nearly all interplant pipelines will be aboveground to minimize the possibility of underground leaks. In addition, the refinery of the future must be prepared to recycle some products, such as used lubricating oil.

REFINERY SYSTEMS

Most refinery processes will be constantly monitored and optimized by advanced computerized controls. Computer systems will be designed to provide quick data feedback and will use an artificial intelligence system to anticipate problems and perform troubleshooting analyses.

Information will be stored on many different systems linked by a network, Support software will be task-oriented with a user-friendly front end to perform low-level systems work. All data and operating and training manuals will be accessible via computer.

To operate these systems, refinery personnel will require much more sophisticated, highly technical training. In-house training centers will be an integral part of refining complexes.

In summary, while the refinery of the 21st century will resemble today's plant in many aspects, it will be cleaner, more sophisticated, and more capital-intensive.

Different refiners undoubtedly will choose different methods to produce the cleaner-burning fuels required by the Clean Air Act and to reduce refinery emissions. But the end result will be a more efficient refinery that makes better use of the crude oil barrel, consumes or recycles most of its own waste, and is more energy efficient.

Copyright 1991 Oil & Gas Journal. All Rights Reserved.