Improving the operation of a lime fume scrubber

The three compartment fume scrubber used screw conveyors to feed lime into the air stream to remove acidic gases. The existing control system had no sensors to determine if the lime was feeding, or at what rate, with the result that the scrubbing was often inefficient and on occasion the feeders would flood and blind the filter bags.

The existing feeders were replaced with metering feeders mounted on loadcell weighing assemblies. Differential pressure transducers were installed to measure the pressure drop across the individual filter compartments.

The addition of a Mitsubishi PLC and an MMI package allowed precise control of the Lime dosing together with improved diagnostics. The resultant savings in manpower and downtime alone gave a one year payback and the improvement in cleaning kept the plants emissions well within statutory requirements.

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