Abstract: A method for indirect gas species monitoring based on measurements of selected gas species is disclosed. In situ absorption measurements of combustion species are used for process control and optimization. The gas species accessible by near or mid-IR techniques are limited to species that absorb in this spectral region. The absorption strength is selected to be strong enough for the required sensitivity and is selected to be isolated from neighboring absorption transitions. By coupling the gas measurement with a software sensor gas, species not accessible from the near or mid-IR absorption measurement can be predicted.

Abstract: A method for conducting laser absorption measurements in high temperature process streams having high levels of particulate matter is disclosed. An impinger is positioned substantially parallel to a laser beam propagation path and at upstream position relative to the laser beam. Beam shielding pipes shield the beam from the surrounding environment. Measurement is conducted only in the gap between the two shielding pipes where the beam propagates through the process gas. The impinger facilitates reduced particle presence in the measurement beam, resulting in improved SNR (signal-to-noise) and improved sensitivity and dynamic range of the measurement.

Abstract: A method and apparatus for monitoring the flue gases of a furnace combustion process is disclosed. A by-pass circuit that communicates a sample of flue gases to be monitored from a furnace, through a measurement chamber and back to the furnace or furnace exhaust duct is provided. The by-pass circuit has a gas sampling probe with a fume inlet opening, the probe being positioned for withdrawing the sample to be monitored and transmitting it through the by-pass circuit. A measurement device is positioned in the measurement chamber and comprises an in situ optical device which provides real-time measurement of targeted flue gas species concentrations.

Abstract: An apparatus and method for simultaneous detection of N gas species through laser radiation attenuation techniques is disclosed. Each of the N species has a spectral absorption band. N laser sources operate at a wavelength &lgr;N in a spectral absorption band separated by the cutoff wavelength for single-mode transmission. Each laser source corresponds to a gas species and transmits radiation through an optical fiber constructed and arranged to provide single-mode transmission with minimal power loss.

Abstract: A method for monitoring the high temperature reducing combustion atmosphere in a combustion process is disclosed. First, a spectral region for monitoring CO and H2O is identified. A laser wavelength is scanned so that a complete absorption transition includes a portion of the baseline. A laser is then referenced to an ITU-GRID. An output signal is generated from the laser and directed to a coupler to split the output signal in a predetermined ratio to a first component and a second component. The first component is directed to optics where it is shaped and collimated and then directed across a sample to be monitored to a detector that generates a measured output. The second component is directed to an absorption measurement device. The measured output is compared with the second component, and the temperature of the atmosphere and the concentration of the CO present in the atmosphere is calculated.

Abstract: Methods and apparatus are presented using tunable diode lasers for monitoring and/or controlling a high temperature process using an oxidizer containing O2 and organic fuel. Real-time monitoring of key species such as O2, CO, and H2O allow determination of the global or local stoichiometry, gas temperature, particulate concentration, and air entrainment levels into the process. Coupling the measured information with a control system provides a means for optimizing and controlling the process.

Abstract: A method for extending the gas lifetime of an excimer laser by removing CF.sub.4 impurity, which comprises:a) reacting CF.sub.4, an undesirable impurity which forms and is contained in the lasing gases, with an amount of an oxidizing gas additive effective to produce one or more compounds which are condensible with refrigeration means, without reducing laser output below a predetermined acceptable level; andb) condensing said one or more compounds produced in step a) with refrigeration means, substantially without condensing said one or more rare gases therewith, thereby removing said CF.sub.4 impurity from said excimer laser and extending the gas lifetime of the laser.

Abstract: In accordance with the present invention, methods and apparatus to control or monitor the combustion of a burner are presented which overcome many of the problems of the prior art. One aspect of the invention comprises a burner control apparatus comprising means for viewing light emitted by a flame from a burner, means for optically transporting the viewed light into an optical processor, optical processor means for processing the optical spectrum into electrical signals, signal processing means for processing the electrical signals obtained from the optical spectrum, and control means which accept the electrical signals and produce an output acceptable to one or more oxidant or fuel flow control means. The control means may be referred to as a "burner computer", which functions to control the oxidant flow and/or the fuel flow to the burner.

Abstract: An oxy-fuel burner according to the present invention includes an outer oxidant tube, an intermediate fuel tube and an inner oxidant tube which are coaxially arranged with the fuel tube disposed between the inner and outer oxidant tubes. Characteristics of the flame produced by the burner may be controlled by varying the relative flow rates of the inner and outer oxidant flows. An increase in the percentage of the total oxidant which is provided to the inner oxidant tube causes the length and luminosity of the flame to decrease and the flame momentum to increase. According to the present invention, the characteristics of a burner flame can be tailored to a particular application without requiring mechanical modification of the burner.

Abstract: Low-level fluorine concentrations are removed from gases by conducting a gas stream containing fluorine over an alumina treated with chromium oxide material, thereby effectively eliminating fluorine from the gas while preventing the formation of toxic oxygen difluoride by-product.