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Show organics. Additionally, there is a temperature window which must be maintained to ensure proper operation, but redu~e slagging, fouling and corrosion problems. Finally, post combustion NOx and S02 control techniques are being considered in WTE sites also. In industrial processes, temperature monitoring is also important for reducing pollutant emission and increasing process efficiency. Also, in many industrial processes, there is a need for flame temperature monitoring and the measurement of material temperatures. For example, successful operation of high temperature industrial processes such as cement kilns, glass tanks, and steel reheat furnaces is very dependent on the flame and material temperatures. Despite the well recognized needs in utility and industrial furnaces, the hostile environment and large range of temperatures present in these processes have lead to the lack of continuous techniques in use today. The most common method utilized to measure gas temperature is a suction pyrometer or high velocity thermocouple (HVT). This technique cannot be used continuously because the radiation shield required are easily plugged by ash and broken due to thermal shock. Thus the shields typically last only minutes in the furnace environment. Also, the probe measures a very local temperature which may not be indicative of the average temperature or trends in the furnace behavior. However, in testing situations where spacial temperature profiles are required, this technique is very suitable. Recentl y, acoustic methods have been developed to measure gas temperature. 1 These pyrometers are based on the speed of sound, and the changes that occur as a result of gas temperature and composition. This technique also suffers from problems, the most important are: the cost of installation, since new furnace waterwall penetration are often required; and interferences due to power plant noise. Mapping of furnace temperature is possible with this technique, but this requires multiple horns and detectors and is rather complex, expensive and difficult to install. Infrared pyrometers have been available for some time. These devices are used to measure radiation emitted by exhaust gases rather than the ash particles. They can be very accurate in well characterized environments. However, temperatures calculated from infrared radiation measurements are subject to fluctuations in the gas emissivity and radiation from walls and particles.2 As a result, these devices have not gained widespread acceptance in utilities. 2. PSIT OPTICAL TEMPERATURE MONITOR PSI Technology Company (PSIT) has been developing a technique to measure temperature in a non-intrusive, continuous manner for combustion systems. The PSIT optical temperature monitor (OTM) is a novel adaptation of radiation pyrometry. The PSIT OTM is a computer-coupled, multi-wavelength pyrometer that senses radiation at wavelengths shorter than those used by infrared detectors. The radiation detected comes from the ash, coal or soot particles entrained in the gas stream. By measuring particle radiation intensity instead of gas radiation intensity, interferences that plague conventional IR 2 |