Automated gas measurement system

#The present invention relates to gas measurement for constituent concentration and flow rate emitted from processes such as burning coal, oil, gas, wood, sewage, hazardous wastes, or venting from noncombustion processes.

#The United States Environmental Protection Agency (EPA) has regulated techniques including reference methods for the measurement of gas constituent concentrations and flow from various processes. These techniques are found in Title 40 of the Code of Federal Regulations. The regulations detail the method to perform testing and report the results. This allows the emissions to be compared on an equal basis between different locations in the U.S. and among various industries.

#Among the procedures to be followed are the measurement of pollutants for a volume of emitted gas at standard conditions. Briefly, standard conditions are determined by the gas flow temperature, "zero flow" pressure, atmospheric pressure, and calculated (average) molecular weight for the constituents to be measured. Also, a sample maintained at a temperature above the dew point of the relevant gases is required for determination of moisture content.

#FIG. 1 is an elevational view of a preferred embodiment of the present invention, illustrating the set of automated probes equidistantly located at the test ports of a smoke stack and also showing the associated portable control and test equipment.

#FIG. 2 is a top plan view of the preferred embodiment of FIG. 1, illustrating the positioning of the four automated probe assemblies about the smoke stack.

#FIG. 3 is a side view of a typical probe assembly in the preferred embodiment of the present invention, illustrating the combination of probe segments, end housing, pitot tube assembly, and support as temporarily installed at each port of the smoke stack.

#The preferred embodiment of the present invention utilizing four probes in a system or probe set is shown in FIG. 1, referenced generally by numeral 20. A combination of valves, motors, transducers, a pitot tube assembly, and a filter, comprise each probe assembly 32, which are designated as 32a-d. The probe assemblies 32a-d include position sensors and are preferably positioned by stepping motors. The probe assemblies 32a-d are controlled using an indexing module that is part of a remote PLC 92 which is in communication with a PLC 156 in a mobile unit 26. A junction box 38 located near the set of probes 20 on a smoke stack 22 contains the remote PLC 92, a heater, air and gas hoses, an air storage tank 89, and valves corresponding to each of the four probe assemblies 32a-d.

#The automated probe set 20 of the present invention is located approximately 5 "diameters" from the inlet of the smoke stack 22, along its height. Although four probes 32a-d are shown comprising the probe set 20, it is to be understood that more or less may be used in the present invention. As can be seen in FIG. 2, for the "typical" probe assembly 32a, a line 37a is used to route the various air and gas tubes from the probe assembly 32a to the junction box 38. A tube bundle 24 including an air tube for purging, a sample gas tube, and a calibration gas tube extends from the junction box 38 down to the trailer or mobile unit 26. The mobile unit 26 contains, among other devices, gas cylinders and gas analyzing equipment, which will be described in detail below.

#The specific configuration of the probe set 20 of the preferred embodiment is seen in FIG. 2. Here, a view downward is shown, from just above the probe set 20 on a smoke stack wall 28, to illustrate the positioning of each probe assembly, such as 32a, through a "standard" port opening 33a, which is typically 4" in diameter. Located proximally at the end of the probe assembly 32a--that is, within an interior 30 of the smoke stack 22--is a pitot assembly 34a. An end housing 36a of the probe assembly 32a is shown at a distal end, and the line 37a extending from the end housing 36a is connected to the junction box 38, along with lines 37b-d of the other probe assemblies 32b-d. Although only one junction box 38 is shown, it is to be understood that more than one may be used in alternate embodiments of the present invention. As will be described in further detail below, support structures 40a-d, indicated in FIG. 2, are used for support of the probe assemblies 32a-d during installation and testing.