Cement Manufacturers Association (CMA)

Page 48 - Pt 100 temperature sensors Pt 100 sensors only give fully reliable information when they are measuring the air temperature, e.g. in a silo. When the sensor is surrounded by coal, the temperature it reliably measures is only the temperature of coal in the area that is less than roughly 120 mm away from the sensor’s probe. Coal is a bad thermo conductor. This means that some interpreting is always necessary, when reading the temperature that is measured in a column of bulk coal. ‘The picture’ is never complete. - Gas analysers The minimum is to have gas analysers monitoring O and the CO of the process air as follows: - O in air inlet of mill - O in air outlet of DC - CO in air outlet of DC - CO in top of PF silo(s) To use ‘chemical’ gas analysers means that frequent recalibration is required, Chemical analysers have a life span of only a very few years. In the industry it can be seen very often that the ‘chemical’ gas analysers are not recalibrated often enough or have surpassed their useful life. ‘IR’ (infrared) gas analysers should be used. When a system is good it will take care of the cleaning and dehydration of the air that passes through the analysers and ensure that the air intake from the coal grinding system’s spots are kept clean. An O and a CO analyser can be installed in line downstream of one cleaning/dehydrating unit. If the suction lines for the air are not too long it is possible to use one set of analysers for the monitoring of 2 or 3 pieces of equipment (e.g. PF silos). An alternating sequence can then be arranged for. When, e.g. in case of high VM coal, the raw coal silos are connected with the emergency inerting system it makes sense to install a combined CO and O analyser. The progress of an emergency inerting process is indicated by the O value. To know the O value and to see it decline in an emergency situation can be helpful. The same is true for the monitoring of PF silos. - Emergency inerting The inerting medium, gaseous CO or N , storage at all times. Many systems with the available quantity can be found, in the industry. Only when the tank or the bundles of gas cylinders are installed with a weighing feature the indication of the storage is reliable. It has to be made the task and the responsibility of the raw coal yard personnel maintenance never reaches a raw coal silo, where it could become the source of very dangerous scenarios. the raw coal in the yard is expected from such vigilance very rarely is subject to written rules that help meet the need for of such a situation. The requirements of met, without written rules being in place. on this.