By Robert S. Giglio
The new administration is taking a hard look at how the United States generates its electricity and powers its transportation and industry. It is banking on a major investment in the power and energy infrastructure to pay off in a future of high-quality green jobs, less reliance on foreign sources of energy, and reduction in the production of greenhouse gases and air pollutants.
The administration’s New Energy for America plan has set the ambitious goal to reduce GHGs by 80 percent by 2050.
Supporting the administration’s goals, the President’s budget includes more than $150 billion over 10 years in clean energy and energy efficiency, and a 10-year commitment to make the Research and Experimentation Tax Credit permanent. The funds support the administration’s position that investments in research and development today will pay off in high-quality green jobs tomorrow.
President Obama’s plan addresses a broad range of energy sectors, but the one area where this subject hits closest to home—and just about every other sector of society—is in the way we generate electricity.
Installing solar, wind, biomass, and nuclear can help reduce emissions, but these technologies, for various reasons, can’t replace the country’s major source of electric power any time soon.
Nuclear energy will be constrained by the length of time it takes to build plants and get the regulatory approvals and by perceived safety concerns. Biofuels and other renewable alternatives—the most practical of which at present are wind and solar power—will grow rapidly, but will remain relatively small contributors and will not replace significant quantities of fossil fuels in the near future.
One place to look to achieve significant reduction in greenhouse gas emissions today is in controlling the emissions of coal.
In the United States, by far the world’s largest energy consumer, coal is burned to generate half the electricity consumed each year and almost a quarter of the country’s total energy consumption. Although coal is a major contributor to the U.S. energy supply, it is also the most carbon-rich of the common fuels in use today.
Practical technology exists today that can reduce the carbon emissions of coal. They include the circulating fluidized bed.
CFB technology sharply reduces emission of harmful pollutants and can cleanly burn traditional coal fuels, as well as “carbon neutral” biomass fuels. A CFB plant built to burn a combination of traditional fuels and several types of biomass fuels can substantially reduce greenhouse gas emissions, while still producing affordable electricity to meet the nation’s needs in this time of economic uncertainty.
What’s more, new upgrades to CFB technology have the potential to transform it into an innovative long-term carbon capture and storage solution, ready to take its place as a clean coal technology called for in the New Energy for America plan.
Unlike conventional steam generators that burn the coal in a massive high temperature flame, CFB technology uses fluidization technology to mix and circulate the fuel particles with limestone as they burn in a low temperature combustion process, as low as 1,500 °F. A pulverized coal-fired plant, the most common in use in the United States, operates at temperatures well over 2,000 °F.
The CFB does not have burners or a visible flame within its furnace. Instead, it uses fluidization technology to mix and circulate fuel particles with limestone as they burn in the relatively low-temperature combustion process. The limestone captures the sulfur oxides as they are formed, while the lower burning temperature minimizes the formation of thermal nitrogen oxides. Unburned fuel and limestone particles are recycled over and over back to the process, which results in high efficiency for burning the fuel by extending the combustion residence time, capturing pollutants, and transferring the fuel’s heat energy into high-quality steam to produce power.
A further environmental enhancement is highly efficient vertical-tube, supercritical steam technology, which allows more of the fuel’s energy to be transferred to the steam. This improves overall power plant efficiency, reducing the amount of fuel needed for electricity production and further reducing air emissions by an estimated 30 percent.
Foster Wheeler has built a supercritical steam system with CFB steam generator in Poland. The renovated plant began operating last July. The combination of CFB and supercritical steam results in an increase in efficiency with reduced emissions compared with the pulverized coal technology that had previously powered the plant.
Due to their unique combustion process, CFBs can be used to burn biomass fuels—for example, forest residue, demolition wood, saw dust, corn husks, and sugar cane. Biomass is considered carbon neutral, since it absorbs and stores carbon from the atmosphere through photosynthesis. When burned, biomass releases the same carbon back to the atmosphere, resulting in nearly zero net CO2 emissions to the atmosphere.
So, if burning biomass reduces CO2 emissions, why don’t we build power plants that burn only biomass? The answer is that the undeveloped biomass supply chain limits the size of biomass power plants to about 25 to 50 megawatts of electricity. We would need ten or more biomass plants to replace each existing large scale (300 MW or larger) power plant. The small scale and fuel supply limitation means that electricity from a biomass plant costs about 20 to 30 percent more than that from conventional large fossil power plants.
Again, the CFB offers a solution. Due to its fuel flexibility, a large-scale CFB power plant can be built to burn a combination of coal and several types of biomass, capturing the environmental benefit of substantially reducing CO2 emissions and the economic benefit of providing affordable electricity. Its flexibility meets consumer demand by using more biomass when available, or falling back on coal when it is not. The good news is that this can be done today, while still producing affordable electricity.
Reductions Beyond 30 Percent
While a 30 percent reduction in CO2 emissions is a big step in the right direction, projections show that we need to do much more to reduce the effects of global warming. So companies including Foster Wheeler are working to develop technologies that can curb carbon and other emissions from combustion even further.
The Obama administration supports incentives to accelerate investment in zero-carbon coal facilities, and the policy includes developing coal-fired plants with carbon capture and storage (CCS), considered key to using our abundant coal supply while mitigating and reducing the effects of global warming. CCS refers to capturing CO2 (one of the Earth’s most abundant GHGs) from coal-fired power plants, and storing it underground, in deep saline aquifers or other geologic formations.
CCS is the direction towards which policy makers and the industry seem to be moving. Companies including Foster Wheeler are developing new flexible combustion technologies to adapt to future needs. A technology called Flexi-Burn, under development by Foster Wheeler, holds promise for dramatically lowering both the cost and technology risk for the CCS solution.
Flexi-Burn steam generators are designed to they can be changed from air-firing to oxy-fuel combustion. A Flexi-Burn boiler would make it practical to use air firing for maximum power output in periods of high load demand, such as summer, weekdays, and daytime, and switch to oxy-fuel combustion with CO2 removal at other times.
These technologies simplify the CO2 capture and removal process by using a mixture of oxygen and recycled CFB flue gas to produce a CO2 -rich flue gas that can be more easily captured. The technology could reduce coal plant CO2 emissions to the atmosphere by more than 90 percent, offering practically carbon-free electricity at a low cost compared to other available technologies.
As shown in Figure 1, a supercritical 600 MW CFB plant burning 20 percent biomass is estimated to produce 32 percent less CO2 emissions than a conventional coal plant.
Meeting Challenges Ahead
Our nation faces critical challenges in meeting the demand for affordable power in an era of economic uncertainty, when stimulating growth is at the top of the priority list. How can we move forward with this need to keep energy prices affordable while at the same time making progress on the ambitious environmental agenda that includes diversifying our energy sources, improving the environment, and reducing the effects of climate change? We will need to use all the tools in our arsenal, including relying on existing technologies that can provide environmentally friendly power at a cost we can handle. As the Obama-Biden energy plan has outlined, no one solution will fit the bill, but with the integration of CFBs into existing and new coal-burning plants we are taking a step towards a brighter future.
National and International Energy Demands
Our country’s struggle to diversify its energy sources is taking place as part of a global energy picture in which demand for electricity is growing as living standards improve and the population increases. The U.S. Department of Energy, Energy Information Administration (DOE/EIA) forecasts that energy demand between now and 2030 will increase by a half, with two-thirds of the new demand likely coming from developing nations.
To meet the existing demand for electricity, and the tremendous likely future demand, we will need to tap deeper into all of the world’s primary energy sources, including nuclear, natural gas, coal, and renewables. The EIA forecasts show that, in the coming decades, more coal and more natural gas are likely to be used than other sources.
Robert S. Giglio is the director of global marketing and strategy for the Foster Wheeler Global Power Group.