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TITLE Composite Sensor System for Monitoring Combustion Exhaust Gas Elements
(Joint Program to Promote Technological Development with the Private Sectors)

qhsd|ltr`rghmn k`anq`snqx in Yokogawa Electric Corporation


We have developed a solid type CO sensor for measuring the remainders of combustible gas such as CO in the exhaust gas of industrial combustion process (where high SO2 and H2O concentrations my be present).

CO concentration is an ideal index for combustion control. If we control the CO concentration at about 200ppm we can get the highest burner efficiency.

Therefore a CO sensor, as reliable as the zirconia oxygen sensor, is highly desired but not have available in the market at present.

Currently two types of non-dispersive infrared light absorption type CO analyzers are being used for large facilities. One method is to use a sampling device, the other uses a direct method to put the infrared light source and detector at both sides of the duct. The first method has a very long dead time and cannot be used for controlling purpose. The latter is not reliable and its maintenance is difficult.

The solid sensor we are currently developing is expected to have much lower installation costs and to be much more reliable.

The main point of the development of the sensor is the durability to SO2.

We are now running the durability test in gas containing 2000ppm SO2 with 16% water. In this gas conventional catalytic sensors die in a few hours.

We also run a test in a 'Mini-plant' where city gas is burnt to obtain data of the behavior of the sensor in various combustion conditions. Here we got a good agreement with the output of an infrared analyzer.

Field tests from fall of '98 are being prepared. We will be installing prototype detectors on the wall of the duct of typical combustion processes.