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Computer Technology Ari Oualitu Monitor Highlighting stringent government regulations The Stak-Tracker directs an infrared beam for control of the environment require indus- across a smokestack exhaust to a reflector and spinoff examples trial firms to install increasingly sophisticated collects the reflected beam. The instrument monitoring equipment for full compliance sends the beam through a dual filter assembly. in thefield of with smokestack emission standards. One such The first filter operates in the general wave- advanced system is the Stak-TrackerTMC EM length range of the target gas. The other filter, computer (Continuous Emission Monitor) Gas Analyzer, which oscillates in and out of the infrared an air quality monitor capable of separating beam, is the target gas cell. When the cell filter technology is the various gases in a bulk exhaust stream and is in the beam, the beam is absorbed by the cell determining the amounts of individual gases at the target gas' specific wavelength before it a system present within the stream. goes through the smokestack exhaust. A detector measures the ratio of the two signals, for analyzing The Stak-Tracker is produced by GE Reuter- which serves as the basic input that enables the Stokes, Twinsburg, Ohio, a subsidiary of patented analysis technique to provide a smokestack General Electric Company, and is supported by measurement of the target gas concentration. the GE Corporate Research & Development The Stak-Tracker can measure up to six gas emissions Center (GE CR&D), Schenectady, New York. components within three seconds. An important element of the Stak-Tracker is a NASA-developed software package that made In the early 1990s, when the GE CR&D was possible the system's advanced analytical helping GE Reuter-Stokes develop the system, technique. This technique is the key to accu- it became apparent that there were no com- rate measurement of minute quantities of mercially-available software tools for modeling certain gases, such as nitric oxide, carbon monoxide and sulphur dioxide, generated in new, low-emission combustors. Developed by Langley Research Center, the method of analysis is a gas filter correlation technique; it measures the concentration of an individual target gas within the bulk stream by determining the degree to which molecules of that gas absorb an infrared beam. Right: A pair of industrial smokestacks equipped with GE ReuterStokes Stak-Trackerg as analyzers; the Stak-Tracker equipment is shown in closeup war right). offering highly accurate measuremats of pollutants fm improved compliance with environmental regulations, the system inegborates so-re technology that originated at Lungley Research Center: the performance of sensitive pollution moni- GFCR code. The GFCR software was incorpo- tors of this type. The developers, however, were rated into the calibration of the Stak-Tracker, aware that Langley Research Center had and the software has found additional use at designed a software system for a Gas Filter GE CR&D for evaluating changes in the Correlation Radiometer (GFCR) that seemed instrument's design and solving other the answer t6 the need. industrial problems. , Two GE CR8eD scientists-Dr. Emily Shu of the Besides its utility as an aid to full compliance Industrial Electronics Laboratory and Dr. M. K. with environmental regulations, the Stak- I I Cueman of the Manufacturing Technology Tracker offers fast response for process control applications and relatively low installation and I Laboratory-visited Langley's Atmospheric j Research Division and received detailed maintenance costs. It is applicable to gas information on the GFCR software, which is turbines, gas, oil, or coal-fired boilers, incinera- I capable of calculating gas absorption even tors, dryers, scrubber controls, kilns and when the gas is present in minute amounts, process heaters used by the power, oil, pulp and which additionally can separate the and paper, iron and steel, non-ferrous metals, interference from a number of coexisting gases cement, glass and other industries. in a stream. The visit led to a GE-NASA Space Act Agreement for exchange of technical TMStak-Tracker is a trademark of General Electric Company. information relative to trace gas measurement. Langley scientists shared their expertise in atmospheric research and helped GE apply the