Measurement of coal levels in power station bunkers is required to schedule filling and to avoid maximum and minimum levels being exceeded. The surface profile changes as the level falls, depending on: bunker/feeder design, lining material, conditions of the bunker and the flow characteristics of the coal. The coal may tend to drop preferentially to one side or comer, or core (funnel) flow may occur, usually above the feeder inlet. Devices have been used to measure the level in bunkers but a number of them are needed to cover adequately the surface and give a good chance of picking up the lowest level in the bunker. The devices currently used for level measurement include: acoustic, capacitance, diaphragm, load cells, rotating paddles, photoelectric, tilting switch, nucleonic and ultrasonic. Best performance from these is when installed in mass flow bunkers where there is a strong correlation between volume stored and storage level. However, with core flow, none of the above are satisfactory as there is no meaningful relationship (1). This paper describes work carried out at Eggborough power station to test and develop novel, cost-effective laser scanning technology that provides real-time on-line data on the surface profile of the coal in the bunker. Initial testing began in June 1998 to assess the feasibility of a single monitor on a bunker. Following the success of this trial, monitors were installed on a full set of bunkers on a single unit. Testing was carried out during the second half of 1999, with the aim of operating the system for several months for the range of coals taken by the station. The DTI Cleaner Coal Technology Programme and the three partners developing the system have supported the work financially.
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