Coal conditioning system

Abstract

The output of a radioactive source is directed through a moving stream of granular material, e.g., coal on a conveyor, and the radiation passing through is sensed by a detector. The detector generates a pulse signal of which the pulse repetition rate varies with the radiation sensed. The pulses generated are counted in a binary counter, and a timer periodically initiates a read-out of and resets the counter to effect successive counting cycles, whereupon the digital count in each cycle is converted to an analog voltage, the magnitude of which is recorded in terms of bulk density of the coal. The recorder controls the addition of water or oil to the coal to, respectively, lower or increase the bulk density of the coal. Controls are included which guard the system from misperforming when a supply of coal has failed, when the depth of coal on the conveyor belt has been lost, and when the coal is so dense that an application of water is required. The system employs a drop of the coal before it passes the source of radiation so as to simulate the drop of coal in an oven to which the coal is normally supplied, thereby to present coal for bulk density control in a condition the same as that applied to the oven. A paddle-wheel assembly may be employed for this same purpose by striking the material as it is dropped past the paddle-wheel assembly. Alternatively, a sled assembly that tamps the coal may be employed for such simulation.