Development of a video-based slurry sensor for on-line ash analysis. Fourth quarter technical progress report, July 1--September 30, 1995

Automatic control of fine coal cleaning circuits has traditionally been limited by the lack of sensors for on-line ash analysis. Although several nuclear-based analyzers are available, none have seen widespread acceptance. This is largely due to the fact that nuclear sensors are expensive and tend to be influenced by changes in seam type and pyrite content. Recently, researchers at VPI and SU have developed an optical sensor for phosphate analysis. The sensor uses image processing technology to analyze video images of phosphate ore. It is currently being used by Texasgulf for off-line analysis of dry flotation concentrates. The primary advantages of optical sensors over nuclear sensors are that they are significantly cheaper, are not subject to measurement variations due to changes in high atomic number minerals, are inherently safer and require no special radiation permitting. The purpose of this work is to apply the knowledge gained in the development of an optical phosphate analyzer to the development of an on-line ash analyzer for fine coal slurries. During the past quarter, a study was conducted to determine if monochromatic illumination could be used as a means of enhancing the differences observed between coal and mineral matter under reflected light. After extensive testing, monochromatic illumination was found to provide no advantages over white light. In fact, white light appeared to provide slightly better resolution of ash content. Initial testing of the sample presentation system at the plant site indicated that froth formation in the sample tube was indeed a problem as predicted by Pittston representatives. A slight modification in the design of the tube and a modification in the time required to bring the slurry level into the focal plane of the camera were found to eliminate the frothing problem