On-stream ash and moisture monitoring in utilities, coking and preparation plants

On-line coal analysis is essential for the monitoring and control of coal preparation operations, for identifying problems in coal handling, blending of coal to meet user specifications and increasing the efficiency of fossil fuel power plants and coking facilities. The hard coal industry in the Federal Republic of Germany has acquired decades of experience with gamma ray backscatter ash gauges. In the past, moisture meters based on microwave phase shift and attenuation measurement were developed, 'commercialized' and brought into industrial operation. More recently, dual energy gamma ray transmission ash gauges are becoming more common in numerous preparation plants. Owing to the unfavourable economic position of the coal industry, one of the major development objectives was low prime cost, especially since the number of instruments needed at a plant site is increasing rapidly. This led to the use of a modular arrangement approach and to the application of freely programmable personal computers that offered the possibility of inserting tailored slot cards and access to many types of available software. As a result, several monitoring systems have been installed, at present mainly in preparation plants. At one mine, a system is operating which includes two backscatter ash gauges, two dual energy gamma ray transmission ash monitors and two moisture meters. Their high degree of availability and sufficient level of accuracy ensure that these instruments are well suited for quality monitoring and process control. (author). 4 refs, 7 figs