Lawrence Livermore National Laboratory demonstrated coal gasification in large-scale field experiments at the Rocky Mountain Test Facility (above) near Hanna, Wyoming. Coal gasification and sequestration of the carbon dioxide produced are among the technologies being used in the Texas Clean Energy Project. | Photo courtesy of llnlphotos.
The Department of Energy is working with industry to keep the United States at the forefront of carbon capture, utilization, and storage technologies. An innovative clean coal demonstration project in Texas, supported by the Department’s Office of Fossil Energy, recently took a big step forward.
The Energy Department announced that CPS Energy of San Antonio will purchase approximately 200 megawatts of power annually from the Texas Clean Energy Project (TCEP) when the facility is complete in 2015. The $2.4 billion plant will receive $450 million in funding from the Department’s Clean Coal Power Initiative; of this, $211 million comes from the American Recovery and Reinvestment Act.
This is the first purchase in the United States of low-carbon power from a power plant that uses carbon capture technology.
When operational, the 400-MW facility located just west of Midland-Odessa, Texas, will be the cleanest coal-fueled power plant in the world. Using a state-of-the-art process known as integrated gasification combined cycle (IGCC), the total amount of carbon dioxide emitted into the atmosphere from this plant will be less than 10 percent of a conventional coal plant with similar energy output, and less than 25 percent of a high-efficiency natural gas-powered power plant.
It will also be capable of capturing 90 percent of the carbon dioxide (CO2) it produces, as well as 99 percent of sulfur dioxide, 90 percent of nitrogen oxide, and 99 percent of mercury.
In the gasification process, coal is not burned as if you were shoveling coal into a furnace or a steam locomotive boiler. Instead, the coal is sealed in a gasifier -- an airtight chamber that allows only controlled amounts of oxygen to enter. Starved for oxygen, the coal bakes rather than ignites and creates enough heat and pressure in the chamber to squeeze hydrogen and carbon monoxide out of the coal. The gases squeezed from the coal are then processed into synthetic gas, or syngas.
Next, water vapor is added to the syngas, which chemically reacts with the carbon monoxide to create additional hydrogen and also carbon dioxide. The gas is then cleaned of impurities, and separated into pure streams of hydrogen and carbon dioxide. The hydrogen powers an advanced turbine to generate electricity and its carbon-free exhaust heats water to generate steam that’s fed to a turbine to produce even more electricity.
Of the nearly 2.9 million metric tons of carbon dioxide to be captured annually at the Texas plant, 83 percent will be used in the West Texas Permian Basin for enhanced oil recovery -- a technique where carbon dioxide is pumped into a known reservoir where it expands and forces the oil out of the well. The rest of the captured carbon dioxide will go to producing urea -- a valuable compound with many industrial applications.
Today, approximately 80 percent of the energy consumed in the United States comes from coal, petroleum, and natural gas, with coal-fired power plants accounting for approximately half of the electricity generated. The implementation of clean, state-of-the-art coal-based technologies will help ensure America’s energy security while mitigating the environmental impacts of fossil fuel use.