Environment, refining needs put focus on IGCC

Leo R. Aalund
Managing Editor-Technology

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The cautious flirtation that the international refining industry has had with integrated gasification combined-cycle (IGCC) technology is getting much more serious.

The need to generate electricity and make petrochemicals and hydrogen from low-value streams is still a driver for employing this technology, but its increasing efficiency, and environmental directives and regulations-especially the global warming issue-are also giving IGCC a big push.

IGCC technical advances and operating experience were addressed at the Gasification Technologies Conference in San Francisco earlier this month. The conference is sponsored by the Electric Power Research Institute (EPRI), Palo Alto, Calif., and the Gasification Technologies Council, Washington, D.C.

Big projects

Gasification feedstocks are low-value, problem streams loaded with sulfur and metals. They include asphalt, vacuum resid, visbroken tar, and petroleum coke. Getting rid of these while making desirable products is a strong point of IGCC.

Ten major refinery projects are in the engineering or construction stage and are slated for start-up in 1999-2001 (see table, p. 42). Two are on stream. They will make electricity, steam, hydrogen, and synthesis gas.

An option is to burn all the hydrogen and syngas in turbines to make electricity. In this case, the waste heat is used to make steam for steam turbines and generate more electricity.

In other cases, the hydrogen will be used in refinery hydrocracking and hydrotreating units, or in ammonia production, while the synthesis gas will be converted to petrochemicals such as ammonia and methanol.

Plant costs, emissions

Foster Wheeler Italiana and General Electric Co. detailed the investment needed to build variously sized IGCC plants, and the resulting emissions from those plants. (Foster Wheeler and Snamprogetti SpA are building a 500-MW IGCC plant at Priolo, Sicily.)

Except for differences in capacity and integration with the air separation unit, all the plants compared follow essentially the same design.

Each of the plants is designed to gasify 5 wt % sulfur-content visbroken tar that is valued at $30/ton. Despite the poor-quality feedstock, the emissions are extremely low, amounting to only 50 mg/cu m of NOx and 10 mg/cu m of SO₂. The sulfur capture efficiency is 99.7%.

Such performance has increased interest in the process because high sulfur levels decrease the value of once- salable fuels and petroleum coke.

The Foster Wheeler comparison showed that the largest plant analyzed, which has a net electric power output of 802 MW, can produce electricity at 3.63¢/kw-hr at an internal rate of return of 12%. For a 15% IRR, the cost jumps to 4.26¢/kw-hr.

For the two cases, the portions of the cost attributable to the investment were, respectively, 1.713¢/kw-hr and 2.153¢/kw-hr. The feedstock component was 0.647¢ in both cases. Maintenance, taxes, chemicals, and personnel account for the rest of the cost.

Carbon dioxide

Many industrialized countries are now committed to reducing CO₂ emissions as a result of the Kyoto protocol on cutting greenhouse gases.

Switching from residual fuel oil and coal to natural gas in fossil fuel-based power generating stations translates into important reductions in CO₂ emissions. Further significant CO₂ emission reductions can be achieved by replacing old and inefficient fossil fuel-fired power stations with advanced IGCC power plants, even though their feedstocks are often very heavy hydrocarbons or petroleum coke. IGCC fuel-to-electricity efficiencies run at 52%.

Dale Simbeck, vice-president of technology, SFA Pacific Inc., Mountain View, Calif., addressed the CO₂ issue in detail in his paper on gasification in a carbon-constrained world.

Simbeck said it is difficult, if not impossible, at this time to answer the question of whether CO₂ emissions cause global warming. It is easier, however, to determine the most cost-effective options for reducing man-made emissions, he said.

That is simple to calculate, he said, with the following relationship:

Number of people x gross domestic product (GDP)/person x energy/unit of GDP x CO₂/unit of energy.

This means there are four basic options to reduce man-made CO₂ emissions: population, standard of living (GDP/person), energy efficiency (energy/unit of GDP), and fuel mix or CO₂ sequestering (CO₂/unit energy).

The greatest potential method of improving energy efficiency, says Simbeck, is replacing the highly subsidized energy prices in certain regions with free-market prices. This has been demonstrated in the former East Germany.

China also must reform energy prices and deregulate energy markets in order to end its massive energy waste and economic inefficiency, Simbeck said.

Nuclear power, biomass, and other renewables have lower net CO₂ emissions than fossil fuels, but all have some major drawbacks. Natural gas is the big "fuel mix" winner, he said.

CO₂ sequestering

The newest issue is sequestering, or "storing," CO₂. Basically this means injecting CO₂ from combustion into depleted oil and gas fields or deep coal seams.

Deep-ocean injection is also being considered.

Shell Nederland Refinery BV is employing an unusual form of CO₂ sequestering. Its Pernis refinery has the world's first application of heavy-residue IGCC fully integrated in a refinery operation. It makes hydrogen, for use in a world-scale hydrocracker, and electricity. The unit has been on line since early this year.

Shell is sending part of the CO₂ it makes to a greenhouse for growing tomatoes, in an attempt to enhance growth. P.L. Zuideveld of Shell International Oil Products BV, Amsterdam, said this is an experimental project made possible because a pipeline to the greenhouse was available.

The simplest, and likely the lowest- cost, sequestering, Simbeck said, is to landfill low-value, fuel-grade coke produced in upgrading heavy oil.

Currently, more than 40 million metric tons/year of coke is produced, having a CO₂ equivalent of about 150 million metric tons/year. This is equivalent to about 2.5% of expected U.S. carbon emissions in 2000.

He concludes that developing nations account for most of the world's growth in CO₂ emissions. Financial and technical assistance from the rich nations to the poorer ones is therefore essential to any real reduction in CO₂ emissions.

"However," he said, "global climate change agendas are generally ignoring the developing nations. Also being ignored are the lowest-cost CO₂ reduction options, even as some of the high-cost options are being aggressively promoted."

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