Chemistry of Energy Sources
Moderator: Michael C. Kerby, Global Chemical Research Manager, ExxonMobil Chemical Company
Speakers: Michael Parker, Technical Advisor, ExxonMobil Production Company
T. Alan Hattan, Koch School of Chemical Engineering Practice, Massachusetts Institute of Technology
With fossil-fuel production at or near its peak and the cost of oil hovering at $100 per barrel, the chemical industry is intensifying its search for alternative energy sources that are more abundant, renewable, and environmentally friendly. Methods that show promise include bio-based fuels, hydrogen fuel, advanced solar systems, and wind. Nuclear energy has certainly received a setback with the disaster at the Fukushima power plant in Japan following a tsunami, but will it still play a role? Meanwhile, innovations that minimize waste from generation to transmission to consumption lead to more efficient energy use.
Innovation Day, Photograph by Conrad Erb
Michael Kerby, global chemical research manager for ExxonMobil Chemical Company, began the session with a short review of the current state of the energy industry. He noted advances in shale gas and clean coal, and gave the audience an overview of the global demand for fuel by year and by projected supply sources (biomass, coal, oil, gas, etc.).
He then turned the floor over to Michael Parker, technical advisor for ExxonMobil Production Company, whose talk was entitled “Natural Gas: An Abundant, Cleaner-Burning Energy Solution.” Parker began by recapping the projection for natural-gas demand. While the total demand for energy was seen as flat in the intermediate term, gas is expected to provide an increasing share of energy from conventional hydrocarbons. Drivers for use of gas include the ability to satisfy peak loads and lower emissions along with security of supply. He then described the typical shale-gas fracturing process in detail, including the physical drilling of the well (directional drilling), cementing, and fracturing of the shale formation. Parker presented information on the composition of the fracturing fluid, which is about 90 percent water, 8 to 9 percent sand, and 0.5 to 2 percent chemical additives. These additives include inorganic acids, sodium chloride, polyacrylamids, surfactants, and biocides. Additional discussion before and after the talk centered on the general process of extraction, the additives in the fracking fluid, and the environmental impact of shale-gas production.
The session was then turned over to T. Alan Hatton from the Koch School of Chemical Engineering Practice at the Massachusetts Institute of Technology (MIT) for his talk, “Mitigating the Carbon Problem: CO2 Capture, Storage, and Conversion.” Hatton opened with a discussion of the sources of increased atmospheric CO2.
Capture from point sources, such as power plants, is an obvious target. He described three major classifications of capture technologies: removal from flue gas (which is 15 percent CO2), removal during gasification of the coal, and removal of nitrogen from the combustion gas before burning.
Hatton discussed flue-gas scrubbing in some detail. The main thrust of current work is to reduce energy load in the scrubbing process. A 500-megawatt plant generates 10,000 tons of CO2 per day. Removing 90 percent of that CO2 takes enough energy to reduce the overall thermal efficiency from 39 percent down to 29 percent, and this shift translates to $50 per ton of CO2 avoided. The goal of current work is $30.
Hatton then described a number of novel removal technologies now being explored:
- different amine systems, including ethanol and diethanol amines;
- use of amino acids;
- chilled ammonia technology;
- biocatalytic enzymes to catalyze the absorption reactions;
- phase-change absorbents (capture with a solid, which is then subjected to a phase change to release the CO2);
- ionic liquids;
- membrane separations, including liquid membranes;
- solid adsorbents, including zeolites with shape-selective pore structures; and
- electrochemical processes (a particular research interest of Hatton’s group at MIT).
Some of the new systems are adversely affected by moisture. There are also attempts to remove CO2 and SO2 together, simplifying the treatment process.
Hatton closed by reviewing options for the sequestration process itself, including disposal in geologic formations, disposal in the ocean, fixing the CO2 in cement, and conversion to a biofuel.