Level Measurement - Bed Level Measurement System
Use of Hawk "ORCA" Sonar Bed/Hindered Level Transmitter to Maximize the Efficiency and Performance of Coal Preparation Plant Tailings Thickeners.
Using the ORCA Sonar bed level transmitter to optimize Coal Tailings Thickeners by controlling both the compact bed level and the hindered/interface layer to maximize efficiency and performance.
By monitoring the two independent interface densities we are able to provide reliable process feedback for:
1. Control of the underflow pump to optimize the bed density
2. Control of the flocculent and coagulant dosing systems if the Clarometer fails
The first process that should be automated on the tailings thickener is the discharge rate of the thickener underflow/tailings disposal pump system to maintain the dense slurry compact bed at the optimum level in the thickener.
By cascading the thickener bed level into the underflow/tailings disposal PID density control loop the feed to the underflow pumps will be of consistent density (as per thickener design) therefore minimizing unnecessary pumping of water to and from the tailings dam.
To also minimize unnecessary pumping of water to and from the tailings dam:
1. The thickener underflow/tailings disposal system should only be initiated on plant start up and after the correct bed level has been established
2. The compact dense bed should only be pumped out of the thickener when the plant is going to be idle for and extended time period.
Note: It maybe necessary to purge the tailings lines using injection water on a thickener shutdown.
A) Control of tailings disposal pump speed and water injection using cascaded density and thickener bed level.
1. Analogue output 1, from the ORCA Sonar controlling the heavy density compact bed interface.
2. The compact bed level output is also used as the datum in conjunction with the hindered/interface layer for providing additional process feedback for controlling chemical dosing and alarms.