BOILER FLUE GAS ANALYSIS WITH QCL ANALYZER USED FOR PAPER MILL COMBUSTION CONTROL AND ESP SAFETY

摘要

Paper Mill Hog fuel boilers present a unique challenge for combustion gas measurement. The Hog boilers burn as fuel, solid hydrocarbon based materials that have very different Carbon and Hydrogen content and thus vary in Btu values. The fuel water content can change from dry natural gas to 30% wet wood waste. The fuels in a Hog boiler could be Bark, waste wood, saw dust, plant waste wood products and/or tires. Natural gas is sometimes used to augment the solid fuels. The fuel in a Recovery boiler is Black Liquor or Red Liquor, the residue of the paper making process. The flue gas is latent with fines. Flue gas measurement is required to be prior to the removal of these fines, thus before an Electrostatic Precipitator (ESP) or bag-house. This paper addresses the Quantum Cascade Laser (QCL) analyzer special design features required for this application that deal with these challenges, specifically: 1. Measures CO, CO_2 and H_2O using mid-IR absorption spectroscopy 2. IR penetration of the opaque flue gas 3. Dynamic Optical Range algorithm for handling the light transmission variations 4. Measurement speed of the mid-IR fundamental wavelength 5. Laser temperature precise control using wavelength feedback algorithm 6. Challenge of protecting the interface windows Dynamic trends from the analyzer from a recent installation at Glatfelter Chillicothe Ohio mill are included and discussed.