By Stephen E. Zitney, Ph.D.
Imagine using a real-time virtual simulator to learn to fly a space shuttle or rebuild your car's transmission without touching a piece of equipment or getting your hands dirty. Now, apply this concept to learning how to operate and control a state-of-the-art, electricity-producing power plant capable of carbon dioxide (CO2) capture. That's what the National Energy Technology Laboratory's (NETL) Advanced Virtual Energy Simulation Training and Research (AVESTAR) Center (www.netl.doe.gov/avestar) is designed to do. Established as part of the Department of Energy's (DOE) initiative to advance new clean energy technology for power generation, the AVESTAR Center focuses primarily on providing simulation-based training for process engineers and energy plant operators, starting with the deployment of a first-of-a-kind operator training simulator for an integrated gasification combined cycle (IGCC) power plant with CO2 capture.
The IGCC dynamic simulator builds on, and reaches beyond, conventional power plant simulators to merge, for the first time, a "gasification with CO2 capture" process simulator with a "combined-cycle" power simulator. Based on Invensys Operations Management's SimSci-Esscor DYNSIM software (http://iom.invensys.com/EN/Pages/SimSci-Esscor_DynSimSuite_DYNSIM.aspx), the high-fidelity dynamic simulator provides realistic training on IGCC plant operations, including normal and faulted operations, as well as plant start-up, shutdown and power demand load changes. The highly flexible simulator also allows for testing of different types of fuel sources, such as petcoke and biomass, as well as co-firing fuel mixtures.
The IGCC dynamic simulator is available at AVESTAR's two locations, NETL (Figure 1) and West Virginia University's National Research Center for Coal and Energy (www.nrcce.wvu.edu), both in Morgantown, W.Va. By offering a comprehensive IGCC training program, AVESTAR aims to develop a workforce well prepared to operate, control and manage commercial-scale gasification-based power plants with CO2 capture. The facility and simulator at West Virginia University promotes NETL's outreach mission by offering hands-on simulator training and education to researchers and university students.
Balancing America's Energy Supply and Demand with Environmental Responsibility
Today most of the energy consumed in the United States comes from coal, petroleum and natural gas. Fossil fuel sources account for approximately 80% of national and international energy production, and coal-fired power plants account for greater than half of the electricity generated in the United States. With increasing global energy demands, coal is expected to play a dominant role in meeting future energy needs.
Why do we use coal? The answer is fairly simple, considering that the United States is home to the largest accessible reserves of coal in the world, accounting for approximately one quarter of the world's coal deposits. Coal is the largest domestically produced source of energy. While estimates vary, it has been projected that the United States has enough coal reserves to last another 200 years. Availability and accessibility, coupled with relatively low cost—particularly in light of other energy sources—are the primary reasons why consumers in the United States benefit from some of the lowest electricity rates in the world.
However, there are trade-offs for inexpensive energy. The use of coal produces emissions that can impact our environment. For example, coal combustion is associated with increased sulfur dioxide, nitrogen oxide and mercury. Coal use also emits CO2, a greenhouse gas that has been prominent in the news due to its association with global warming. Significant advances have been made to reduce environmental contaminates resulting from coal usage, and ambitious efforts are underway to advance new technologies to burn coal more efficiently while minimizing environmental impact. NETL and its partners have undertaken a variety of strategic initiatives to explore ways of capturing and permanently storing CO2 as a way to reduce CO2 release into the atmosphere.
The Role of AVESTAR in Accelerating Clean Coal Technology
Relative to power efficiency and environmental conservation, gasification technology represents the future for coal-derived electricity. Simply defined, gasification is a process that uses heat, pressure and steam to convert coal into a synthesis gas (also known as syngas), which is mainly hydrogen and carbon monoxide. The syngas is cleaned to remove impurities and sent to a gas turbine where it will undergo combustion to produce electricity. The hot exhaust gas from the gas turbine is used to generate steam, which is then fed to a steam turbine to produce additional electricity. This process is known as IGCC because a coal-fired gasification process is integrated with a combined cycle system that produces electricity from both a gas turbine and a steam turbine driven by the gas turbine's exhaust.
Compared to traditional power plants, IGCC offers many advantages, including increased power plant efficiency, resulting in lower-cost electricity. Because gasification occurs at higher temperature and pressure, with limited oxygen, environmental contaminants are easier to remove from the flue gas stream. The system also makes it possible to concentrate CO2, providing for more efficient removal. Aside from coal, a wide range of carbon-containing materials, such as petroleum coke and biomass, can be used to produce syngas. In addition to being used for electricity, syngas can be converted to other end products, such as specialty chemicals, clean hydrogen and transportation fuels. Coal gasification electric power plants are now commercially operational in the United States and other nations, and energy experts predict that this process represents the future of clean coal technology.