Limestone Slurry Tank Level Measurement in FGD Systems

Limestone slurry preparation and storage tanks combine agitation, abrasive solids, splashing, foam and deposits. Non-contact radar can reduce exposure to abrasive slurry, but it still needs a clear representative surface and a process connection that will not pack with material. Instrument accuracy on a data sheet is less important than installed echo margin and maintainable geometry.

Define slurry and operating states

Record solids concentration, particle size, density, temperature, pH, additives and expected variation. Include water filling, powder addition, mixing, recirculation, standby, washdown and drain-down. Each state can create a different surface and deposit pattern.

Specify whether level supports mixer protection, pump control, overflow prevention or inventory. Density-based hydrostatic references may change with concentration, so choose acceptance evidence carefully.

Avoid vortex and moving internals

Map mixer shaft, blades, baffles, recirculation returns and inlet jets. Avoid the vortex centre and direct splash zone. Plot the radar beam against all moving and fixed structures at every required level.

A position close to the wall may see buildup or surface climbing. Select the location from actual flow pattern and control duty, then verify it during operation rather than when the mixer is stopped only.

Keep the process connection usable

A long narrow nozzle can trap slurry and generate a strong near-field reflection. Follow antenna projection and nozzle limits for the exact instrument. Provide safe access for cleaning and keep guards, spray rings and insulation outside the beam.

Review condensation and wash water. An approved purge or rinse may help some installations, but uncontrolled water can dilute product, spread deposits or create a hazardous maintenance practice.

Address abrasion and corrosion

Non-contact radar avoids a submerged probe, yet antenna face, flange, gasket and nearby structure remain exposed to splash and vapour. Confirm material compatibility with slurry chemistry, cleaning agents and gas phase.

Protect the mount and cable from vibration and abrasive impact. Inspect liners and nozzle condition because changes around the connection can alter both mechanical integrity and the echo pattern.

Handle foam and signal validity

Clarify whether the required value is foam top or liquid-slurry surface. Foam structure changes with reagent quality, air entrainment and mixer speed. Test representative conditions and save echo curves rather than assuming radar always penetrates foam.

Configure lost-echo, held-value and quality indication so the PLC cannot treat an invalid surface as healthy. Damping should stabilize normal turbulence without delaying a real rapid rise beyond the alarm requirement.

Commission the operating sequence

Verify low, normal and high levels through local display, output, PLC and HMI. Test mixer, refill and recirculation states and independently verify alarm response. Record solids concentration and mixer speed with each reference point.

Inspect early for buildup and bracket movement. Use as-found deposits and signal trends to establish cleaning intervals and reassess after reagent or operating changes. Confirm the measurement result again under load after a shutdown and restart, when settled solids and dried splash can create conditions absent during initial water testing.

Engineering checklist

Record slurry concentration and process sequence.
Map mixer, vortex, baffles and return flow.
Prevent nozzle packing and recessed buildup.
Verify splash-exposed materials and mounting.
Define foam target and invalid-signal handling.
Test alarms with mixer and pumps operating.

Frequently asked questions

Is radar unaffected by slurry abrasion?

It avoids a submerged probe, but exposed antenna, flange and mounting still require protection and inspection.

Should radar be installed above the vortex centre?

Usually not; the vortex can be unrepresentative and unstable.

Can hydrostatic level verify radar?

Only with a density correction supported by the actual slurry concentration and temperature.

Need a project-specific review? Send process data, drawings, photographs and acceptance criteria through our contact page.