Combustion of Refinery Residues in a CFB-Combustor: Measurement of Intermediate Species Using FTIR

Investigations have been performed to show the feasibility of burning refinery residues (calcined petroleum coke and liquid residues) in a circulating fluidized bed combustor. These experiments were done in a CFBC system with a thermal capacity of 100 kW. The unit has been equipped with an additional dosing system for liquid fuels including a newly developed fuel lance. The pollutant formation characteristics are determined using axial profile measurements at 19 different ports along the combustion chamber. To optimize the combustion process and to minimize gaseous pollutants, several operating parameters of the system are varied independently. These parameters are the primary to secondary air ratio, the global air to fuel ratio, the residence time in the primary zone, the overall temperature of the combustion chamber and the Ca/S ratio. Measurements of the flue gas components O₂, C_xH_y, CO, CO₂, H₂, NO_x, N₂O, NH₃ and SO₂ are performed by standard gas analysing techniques. It is important to note that the system is equipped with a Fourier Transform Infrared Spectrometer (FTIR) to qualitatively and quantitatively determine selected gaseous species which are essential for the formation and consumption of N₂O and other pollutants. The gas species measured by FTIR-Spectroscopy are CH₄, C₂H₂, C₂H₄, C₂H₆, C₃H₆ and C₃H₈. Also the important precursors for the NO_x-formation HCN and NH₃ are examined with the FTIR-Spectrometer. The investigations demonstrate that (liquid) refinery residues can be burned successfully as a monofuel within the circulating fluidized bed combustor. The emissions of all pollutants detected are at a low level.