NSF Award
9022383
Heat recovery in utility boilers is maximized when a particular temperature distribution within the furnace and its downstream heat recovery apparatus is maintained. This design temperature distribution provides the optimum balance between steam production by radiant heat transfer in the furnace section and steam reheating or superheating in the convective heat transfer section. When the temperature distribution deviates from its design condition, turbine efficiency declines either because: a) the steam production is too low due to insufficient heat absorption in the furnace; or, b) not enough sensible heat remains in the exhaust to superheat the steam (since too much heat is absorbed in the furnace). Off- design operation can also lead to tube overheating failures, ash deposition, and cold-end corrosion. This SBIR project continues the development and testing of a non-intrusive rapid-response instrument able to monitor ash particle temperatures in furnace exhaust gases. Because the particles are thermally equilibrated with the gas, the measurement is, in fact, an accurate representation of the local gas temperature. The instrument employs an innovative variation of two-color pyrometry to eliminate errors, associated with radiation from the primary combustion zone and boiler walls, which have confounded previous attempts to accurately measure exhaust gas temperatures. The prototype instrument will be coupled to a furnace control system and, after verification of proper operation, used to control and optimize one aspect of the combustion process. This will lead to increased plant efficiency. The instrument can also be used to control incinerator furnace temperatures, specifically to maintain them above 1700oF in order to minimize emission of toxic organics such as aromatic hydrocarbon or chlorinated dioxin/furans. Indirect benefits of the device include increased plant longevity, reduced pollutant emissions, and the extended lifetime of our finite fossil fuel resources. As part of this program, an instrument for calibrating furnace exhaust gas spectral signatures is also being built. This instrument will be useful for acquiring data needed to commercialize the temperature monitor.
