Coal Combustion and Gasification

The combustion of coal provides approximately half of the electric power supply in the U.S. and represents our largest strategic energy reserve. However, the traditional process of burning coal in boilers to drive steam turbines is relatively inefficient, with a maximum overall efficiency of approximately 38%. It also tends to produce substantial emissions of nitrogen oxides (NO_x) and sulfur dioxide (SO₂), which contribute to the formation of ozone and acid rain. For many years, Sandia researchers have used advanced laser diagnostics and optical techniques to investigate the complex, coupled chemistry and physics associated with coal devolatilization, char combustion, NO_x formation, and fly ash formation and deposition. This research has led to significant advances in the understanding of these processes and how they relate to pollutant formation and important operational issues in modern, pulverized coal-fired power plants.

Recently, there has been increased focus in the U.S. and internationally on the development of high-efficiency, ultraclean processes for converting coal to electricity or hydrogen. As a consequence, Sandia is conducting research on two of the most promising processes for utilizing coal: oxy-fuel combustion and coal gasification. In support of this work, a new laboratory is being constructed to allow the investigation of pressurized coal combustion and gasification. Research on coal combustion and gasification at Sandia is led by Chris Shaddix and Linda Blevins.


Coal Combustion Research
Sandia's coal research program utilizes both the Multi-Fuel Combustor (MFC) and the Char Combustion Laboratory (CCL). Research in the MFC focuses on the poorly understood mechanism of NO_x production during the char combustion phase of pulverized coal combustion. Novel techniques for quenching gas-phase reactions under these conditions have been recently developed as part of this research. In the CCL, coal char reactivity and elemental release rates are being measured under oxygen-enriched and CO₂-enriched combustion conditions. This latter research is being conducted in collaboration with the Canadian Mining and Energy Technology (CANMET) research laboratory in Ottawa, Ontario, to determine the feasibility of retrofitting existing pulverized coal powerplants to burn coal in a mixture of oxygen and recycled flue gas, as a means of enabling carbon sequestration of CO₂ in the exhaust stream. Funding for this research is provided by the DOE Office of Fossil Energy, through its National Energy Technology Laboratory (NETL).

Coal Gasification Research
Coal gasification offers advantages over traditional coal combustion technology in the areas of thermal efficiency (when coupled with a gas turbine combined-cycle power plant), reduced emissions, and the ability to generate hydrogen or other high-value fuels or chemicals. Although small-scale coal gasification has been used in the petrochemical industry for decades, the proper design and operation of large-scale units for utility power production is poorly understood. Sandia is using its expertise in laser and optical diagnostics and chemical kinetic modeling to perform the first measurements of coal char gasification kinetics at high-temperature, pressurized conditions. These measurements will allow more accurate computational fluid dynamic (CFD) modeling to be performed for the design and operation of high-temperature gasifiers.