Situ multi-channel combustion gas analyzer

Apparatus for measuring multiple component interfering gases contained in flue gases issuing from a stack due to combustion, comprising:

• a probe for mounting to extend through the wall of a stack including a measurement cavity through which combustion gases in the stack can circulate;
• a transceiver mounted to said probe externally of said stack including an optical portion and an electric circuit portion,
• said optical portion having a light source and a rotary filter wheel with a narrow band filter corresponding to the primary absorption wavelength of each gas of interest for a selected number of separate gas measurement channels, a reference channel, and a total absorption channel, for projecting a succession of beams of light of different selected wavelengths one at a time into said probe, and a detector for continuously detecting any attenuation of the light beams by said gases in said probe for providing a measure of the extend of absorption of each gas of interest in each of said channels, said total absorption channel eliminating background noise and drift and said zero absorption channel providing a reference for the other channels,
• said electric circuit portion providing an electric output representing each of said absorption measurements;
• and
• a control unit coupled to said transceiver including first computing means for continuously converting said electric output to a corresponding percent modulation output for each of said gases of interest and second computing means for continously correcting each of said percent modulation outputs for temperature, for correcting each said output for pressure and moisture, for correcting said percent modulation output for interference between measured gases, for correcting said percent modulation output for non-linearity, for calibrating, ranging and averaging each of said percent modulation outputs, and to provide corrected continuous outputs representing the concentration of each of said measured gases,
• said control unit including an automatic calibration means for continously purging said measurement with dry air to provide zero value that are used in calculating said percent modulation and means to couple a gas valve into said measurement cavity for the purpose of obtaining a gain factor for continuously correcting the measured results.

Apparatus for measuring multiple component interfering gases contained in flue gases issuing from a stack due to combustion, comprising:

• a probe for mounting to extend through the wall of a stack through which combustion gases in the stack can pass;
• a transceiver mounted to said probe externally of said stack including an optical means and electric circuit means;
• said optical means having a chopped light source for projecting beams of light of different selected wavelengths into said probe, a detector for detecting any attenuation of the light beams by said gases in said probe for providing a measure of the extend of absorption of each gas of interest in each of a plurality of separate channels, and a zero absorption channel providing a reference for the other channels,
• said electric circuit means providing an electric output representing each of said absorption measurements;
• and
• control means coupled to said transceiver including first means for converting said electric output to a corresponding percent modulation output for each of said gases of interest, for correcting each of said percent modulation outputs for temperature and pressure, for correcting said percent modulation output for interference between measured gases, and to provide corrected outputs representing the concentration of each of said measured gases,
• said control means including a programmed digital computer using a table iterative solution having channel percent modulation with respect to gas concentration output for a family of temperatures of each of said measured gases.

Apparatus for measuring multiple component interfering gases contained in flue gases issuing from a stack due to combustion, comprising:

• a probe for mounting to extend through the wall of a stack through which combustion gases in the stack can pass;
• a transceiver mounted to said probe externally of said stack including an optical means and electric circuit means,
• said optical means having a chopped light source for projecting beams of light of different selected wavelengths into said probe, a detector for detecting any attenuation of the light beams by said gases in said probe for providing a measure of the extend of absorption of each gas of interest in each of a plurality of separate channels, and a zero absorption channel providing a reference for the other channels,
• said electric circuit means providing an electric output representing each of said absorption measurements;
• and
• control means coupled to said transceiver including first means for converting said electric output to a corresponding percent modulation output for each of said gases of interest, for correcting each of said percent modulation outputs for temperature and pressure, for correcting said percent modulation output for interference between measured gases, and to provide corrected outputs representing the concentration of each of said measured gases,
• said control means providing a compensated CO measurement value equal to ##EQU4## that is insensitive to the dilution effects of excess air.

Apparatus for measuring multiple component interfering gases contained in flue gases issuing from a stack due to combustion, comprising:

• a probe for mounting to extend through the wall of a stack through which combustion gases in the stack can pass;
• a transceiver mounted to said probe externally of said stack including an optical means and electric circuit means,
• said optical means having a chopped light source for projecting beams of light of different selected wavelengths into said probe, a detector for detecting any attenuation of the light beams by said gases in said probe for providing a measure of the extend of absorption of each gas of interest in each of a plurality of separate channels, and a zero absorption channel providing a reference for the other channels,
• said electric circuit means providing an electric output representing each of said absorption measurements;
• and
• control means coupled to said transceiver including first means for converting said electric output to a corresponding percent modulation output for each of said gases of interest, for correcting each of said percent modulation outputs for temperature and pressure, for correcting said percent modulation output for interference between measured gases, and to provide corrected outputs representing the concentration of each of said measured gases,
• said control means providing an efficiency measurement value %CE=%CE Dry flue gas.times.%CE combustibles.times.1/100 where:
• %CE Dry flue gas=K.sub.1 [0.964+0.000135% EA) - (0.000207+1.68.times.10.sup.-6 .times.%EA) T.sub.s ]100
• T.sub.s =flue gas exit/stack temperature .degree.F. K.sub.1 =fuel sensitivity factor;
• oil=1.0, Natural gas=0.91 ##EQU5## % O.sub.2D =% dry oxygen ##EQU6## K.sub.2 =Ratio of total heat loss to all unburned combustibles to that only due to CO, ideally unity
• CO=ppm of carbon monoxide corrected to dry basis stoichiometric conditions.