Lime, powdered activated carbon, dry polymer, soda ash and ferric sulphate are often cheapest bought as powder — but a dry chemical is useless until it is metered accurately and made into a consistent solution or slurry. Dry dosing pairs a volumetric or gravimetric feeder with a make-up system, and lives or dies on dust control, anti-bridging design and reliable wetting.
Powders bridge, rat-hole, absorb moisture and cake — so the feeder, not the chemistry, is usually what limits a dry dosing system. A volumetric feeder (screw or rotary valve) sets a fixed volume per revolution; a gravimetric loss-in-weight feeder weighs the actual mass discharged and corrects in real time for density variation, giving far tighter accuracy where dose precision matters. Downstream, the powder must be wetted into a stable solution or slurry — lime to milk-of-lime, dry polymer through a controlled wetting head, PAC into a slurry tank — before it ever reaches the process. We design the whole chain: storage, feeder, make-up, and the slurry/solution dosing pump.
| Feeder | Principle | Accuracy | Best for |
|---|---|---|---|
| Screw (auger) volumetric | Fixed volume per rev | ±2–5% | Steady-density powders, lower cost |
| Rotary valve volumetric | Pocketed rotor | ±2–5% | Free-flowing powders, dust seal |
| Loss-in-weight gravimetric | Real-time weigh & correct | ±0.5–1% | Precision dosing, variable density |
| Belt gravimetric | Weighed belt | ±1% | High feed rates |
Feed rates from 0.5 to 5,000 kg/h, sized to the reagent and duty.
Sealed transfers, bin vent filters and enclosed wetting protect operators and stop caking from moisture pick-up.
Bin activators, vibrators or live-bottom hoppers keep cohesive powders (lime, PAC) flowing to the feeder.
Wetting heads and eductors disperse powder into water without fish-eyes or lumps — critical for dry polymer.
Polymer needs ageing time; lime needs slaking/mixing — make-up volume sized for residence.
Progressive-cavity or peristaltic pumps handle abrasive lime milk and conditioned slurries with low pulsation.
Silo with bulk delivery for high usage; bag tip stations with dust hoods for smaller plants.
pH correction and metals precipitation as milk-of-lime.
Taste, odour and micropollutant adsorption as a slurry.
Flocculant for clarification and dewatering after make-up.
Alkalinity and pH adjustment.
Coagulant where dry purchase is economic.
Specialist powders for targeted removal.
Tell us the reagent, the feed rate and the duty — we will design the feeder, make-up and slurry dosing to match, with dust and flow problems engineered out from the start.
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