Natural gas and oil fired boilers and space heaters represent a large use of fossil fuel energy in this country. The more heat that can be removed from the combustion gases, the more efficient the unit is and the lower the costs of operation. Higher efficiency also means less fuel fired and lower carbon emissions. However, burning fossil fuels creates more than just carbon dioxide.
Sulfur compounds in trace amounts even in natural gas oxidize during the combustion process into sulfate (SO4). When cooled to around 260°F, sulfate vapors will condense into sulfuric acid that corrodes heat transfer surfaces – a process called cold end corrosion. In many boilers and some space heaters, exhaust gases are maintained at or above 300°F to prevent this. In condensing heaters and boilers, special materials are used to reduce corrosion potential, but there still are problems.
Scientists at Oak Ridge National Labs (ORNL) have developed a type of catalytic converter for natural gas fired furnaces in homes that can remove sulfur from the gases and catalyze carbon monoxide into carbon dioxide. The filter uses titanium dioxide, copper oxide, and a small amount of platinum to react the sulfur and CO in the combustion gases – a process called acidic gas reduction (AGR). In the future, condensing furnaces will last longer and all boilers/furnaces can operate at lower exhaust temperatures. This improves efficiency and lowers carbon emissions for home heating and industrial boilers. – Steve Terry, DTC HVAC & Refrigeration Instructor
