OCR Text |
Show dependence results from chemiluminescence of excited state chemical species, continuum emission from atom molecule reactions, and/or continuum emission from the presence of particles either being entrained or formed in the flame. Other factors that influence the observed spectrum intensity are burner, e.g., mixing intensity of fuel and oxidizer, furnace, e.g., background contributions and entrainment of chemical species into the flame, and optical system, e.g. collection efficiency. Therefore the flame radiation intensity observed in a process can be expressed as a multivariable function lx(t)= \\\f{B,S(t),P(t),OC,OD,F,0,p{t))dV (l) where h is the observed intensity at wavelength A, integrate over the sample volume. This intensity is a function of the burner (B) characteristics, combustion stoichiometry (S), burner power (firing rate) (P), optical collection system (OC), and optical detector (OD), fuel (F), oxidizer (O), and process (p) disturbances. The process disturbances p accounts for the spectral dependence of the flame coupled to the process. These disturbances may result from particulate matter or chemical species entrained into the flame. In addition the variables S, P and p are considered time dependent. For example, in turbulent diffusion flames the mixing between fuel and oxidizer at a fixed location in the flame will vary with time, i.e., the local stoichiometry (S) and firing rate (P) are changing randomly within some range. The variable p may also be considered time dependent, e.g., transient particle entrainment into the flame resulting from material injection into the process. For general process control applications of a burner the variables OC , OD, B, F ,0, and p are fixed, e.g., the burner configuration, collection optics, optical detector, fuel, and oxidant are not changed once the system is in place. With these assumptions E Q . (1) reduces to the following <M')>= \\\f{S{t),P(t))dV (2) 8 |