Wet Scrubber
Acid gases, sticky dust and condensing vapours — cleaned in one pass.
Wet scrubbers use liquid contact — water, caustic solution or acid — to simultaneously capture particulate matter, absorb acid gases and cool hot gas streams. They are the only viable technology when gas contains HCl, SO₂, HF or NH₃ alongside moisture that would blind a fabric filter, or when the dust is hygroscopic, sticky or explosive in dry form. Lozzar designs Venturi, packed-bed and spray-tower scrubbers in PP, FRP, duplex SS or rubber-lined carbon steel for continuous duty up to 500,000 Nm³/h.
How Wet Scrubbing Works
Dirty gas enters the scrubber body and is brought into intimate contact with scrubbing liquid through one of three mechanisms. In a **Venturi scrubber**, gas is accelerated to 60–90 m/s through a converging throat; liquid is injected at the throat and atomised into fine droplets by the high-velocity gas. Inertial impaction and diffusion capture particles down to 0.5 µm while the high liquid surface area absorbs soluble gases. The liquid-gas mixture enters a cyclonic separator where droplets are separated and recycled.
In a **packed-bed scrubber** (counter-current tower), gas flows upward through structured or random packing while liquid flows down from overhead nozzles. The large wetted surface area (200–300 m²/m³ for structured packing) provides long gas-liquid contact time — ideal for high-efficiency absorption of HCl, SO₂, HF or NH₃ with NaOH, Na₂CO₃ or dilute H₂SO₄ as the scrubbing reagent. Absorption efficiency depends on mass-transfer coefficient (KGa), packing height (HTU × NTU calculation), liquid-to-gas ratio (L/G = 2–10 L/Nm³) and equilibrium chemistry.
In a **spray-tower scrubber**, liquid is atomised through full-cone nozzles into a large open vessel. The low gas velocity (1–3 m/s) and large droplet size make this design best for high-dust-load gas cooling and coarse particle scrubbing (d₅₀ > 20 µm) before a packed-bed stage. Spent scrubbing liquid is neutralised, settled and either recycled (closed-loop zero-liquid-discharge) or discharged to effluent treatment. Mist eliminators — chevron or mesh-pad type — remove entrained droplets before the clean gas exits to atmosphere or continues to a fan.
Quick Reference
Technical Specifications
All parameters are indicative ranges. Final sizing is determined by process simulation based on your specific material and throughput requirements.
Operating Parameters
| Parameter | Value / Range | Note |
|---|---|---|
| Gas flow range | 500 – 500,000 Nm³/h | Multi-unit arrays up to 2,000,000 Nm³/h |
| Inlet gas temperature | Up to 1,000°C | Quench section cools to <70°C before packed bed |
| Inlet dust load | Up to 50 g/Nm³ | Venturi handles > 50 g/Nm³; cyclone pre-separator recommended > 20 g/Nm³ |
| Outlet particulate | <20 mg/Nm³ (guaranteed) | Venturi: <50 mg/Nm³ typical; packed-bed + mist eliminator: <5 mg/Nm³ |
| HCl removal efficiency | >99.5% (packed bed, NaOH) | SO₂: >95%; HF: >99%; NH₃: >98% with H₂SO₄ |
| Scrubbing liquid L/G ratio | 2 – 10 L/Nm³ | Lower for cooling only; higher for high-concentration acid gas |
| Pressure drop | 500 – 3,000 Pa | Venturi: 1,500–5,000 Pa; packed-bed: 500–1,500 Pa per metre |
| pH control range | 1 – 13 | Automatic dosing of NaOH or H₂SO₄; ±0.2 pH accuracy |
| Construction materials | PP / FRP / SS 316L / Rubber-lined CS / Duplex | Selected per pH, temperature and gas chemistry |
| Effluent treatment | Neutralisation + settling + closed-loop recycle | Zero-liquid-discharge (ZLD) option available; cake disposal by filter press |
Scrubber Type Comparison
| Parameter | Value / Range | Note |
|---|---|---|
| Venturi scrubber | η_particle: 90–97% (>1 µm); ΔP: 1,500–5,000 Pa | Best for high-dust, hot, sticky or abrasive gas; simultaneous cooling + scrubbing |
| Packed-bed scrubber | η_acid: >99.5% HCl; ΔP: 500–1,500 Pa/m packing | Best for high acid-gas removal; requires clean inlet gas (<0.5 g/Nm³) |
| Spray-tower scrubber | η_particle: 60–80% (>10 µm); ΔP: 100–500 Pa | Best for pre-cooling, coarse particle removal and high-moisture gas; lowest ΔP |
| Venturi + packed-bed (2-stage) | η_particle: >99%; η_acid: >99.5%; outlet <5 mg/Nm³ | Standard for HWI, glass furnace, hazardous waste — highest total removal |
| Mist eliminator | Chevron: >99% droplets >20 µm; Mesh-pad: >99% >5 µm | Mandatory downstream; prevents carryover of acid mist to stack |
| Closed-loop ZLD system | Blowdown: <5% of recirculation volume | Evaporative crystalliser recovers salts (NaCl, Na₂SO₄, CaSO₄) as dry product |
Need a technical pre-sizing? Send us your material data sheet, moisture content, required throughput and energy source — we return a technical sizing with drum dimensions and energy balance within 2 business days.
→ Send process data on WhatsAppApplication Examples
Reference data from industrial installations. Actual values depend on feed consistency, particle size distribution and required product quality.
| Material | Inlet moisture | Outlet moisture | Particle size | Gas temp. | Industry |
|---|---|---|---|---|---|
| HCl pickling line exhaust | Saturated (100% RH) | Saturated (demisted) | Acid mist 0.5–10 µm | 50–70°C inlet | Steel / Metal Finishing |
| Glass furnace flue gas (SO₂ + HCl + dust) | 15–25% v/v H₂O | Saturated (demisted) | 0.5–50 µm | 300–450°C (after quench: <70°C) | Glass Manufacturing |
| Municipal solid waste incinerator (HCl, SO₂, HF, dioxins) | 20–35% v/v H₂O | Saturated (demisted) | Sub-µm to 50 µm | 200–300°C (after quench: <70°C) | Waste Management / Energy Recovery |
| Chlorinated chemical reactor vent (HCl + organics) | 0–5% v/v H₂O | Saturated (demisted) | Gas-phase only (no particles) | 20–120°C | Fine Chemicals / Pharmaceuticals |
| Fertiliser plant NH₃ recovery (NH₃ + ammonium dust) | 5–15% v/v H₂O | Saturated (demisted) | 10–500 µm | 60–120°C | Fertiliser / Agrochemical |
| Spray dryer exhaust (sticky fine particles + moisture) | 8–20% v/v H₂O | Saturated (demisted) | 1–50 µm (hygroscopic) | 80–120°C | Food / Dairy / Detergents |
| Phosphoric acid plant tail gas (HF + SiF₄ + P₂O₅ mist) | Saturated | Saturated (demisted) | 0.1–5 µm mist | 60–90°C | Phosphate / Mining |
| Rotary kiln exhaust — lime / cement (SO₂ + dust) | 5–15% v/v H₂O | Saturated (demisted) | 0.5–100 µm | 150–350°C (after quench: <70°C) | Cement / Lime / Building Materials |
Don't see your material? Send us your process data and we'll provide material-specific sizing.
Scrubber Configurations
Venturi Scrubber (VS)
Adjustable-throat Venturi followed by cyclonic separator and recirculation tank. Gas velocity at throat 60–90 m/s. Handles inlet dust loads up to 100 g/Nm³ and gas temperatures to 1,000°C. Constructed in PP, FRP or rubber-lined carbon steel. Throat pressure drop 1,500–5,000 Pa. Particle collection down to 0.5 µm at high ΔP setting.
Packed-Bed Scrubber (PBS)
Counter-current column packed with Pall rings, Raschig Super-Rings or structured packing (25–50 mm). Designed by NTU–HTU method for target outlet gas concentration. Single or multi-stage (2–3 stages with inter-stage pH control). FRP, PP or SS 316L construction. Automatic pH dosing (NaOH, Na₂CO₃, H₂SO₄, NaHSO₃). Designed for inlet gas <0.5 g/Nm³ dust (Venturi pre-scrubber if higher).
Two-Stage Venturi + Packed-Bed (VS+PBS)
Stage 1 Venturi quenches and pre-scrubs hot high-dust gas; stage 2 packed bed achieves high acid-gas removal. Mist eliminator at top. This combined arrangement is mandatory for hazardous waste incineration (EU WID Directive), glass furnaces and cement kilns where both particulate and acid-gas emission limits apply simultaneously. Outlet: <5 mg/Nm³ dust, <10 mg/Nm³ HCl, <50 mg/Nm³ SO₂ (EU IED compliant).
When to Choose a Wet Scrubber
Gas contains HCl, SO₂, HF, NH₃ or other soluble acid/alkaline gases at any concentration
Wet scrubber is the only technology that absorbs soluble gases — bag filters and cyclones have zero removal efficiency for gas-phase contaminants.
Dust is sticky, hygroscopic or would bridge/blind a fabric filter at operating conditions
Venturi scrubber handles any dust that would fail in dry filtration — sticky food powders, hygroscopic salts, adhesive resin particles.
Inlet gas temperature exceeds 280°C and a bag filter would require expensive pre-cooling
Venturi quench section cools gas from kiln temperature to <70°C in one step — eliminates separate heat exchanger capital and maintenance cost.
Process gas contains combustible vapours or explosive dust (Kst > 0) that create ATEX risk in dry filtration
Wet scrubber vessel operates in a fully saturated, inerted atmosphere — no ATEX zone within the vessel, no explosion venting panels required.
When NOT to Use a Wet Scrubber
Gas is dry, outlet dust < 5 mg/Nm³ is required, and there are no acid gases — dry filtration is simpler and cheaper
Coarse particle pre-separation is needed before a fine filter — no acid gases, no moisture risk
Product must be recovered dry and waste water generation is not acceptable (no on-site effluent treatment)
Very large gas volumes (>500,000 Nm³/h single unit) at moderate temperatures with dry dust only
Not sure which dryer is right for your process? We'll review your specifications and recommend the optimal solution.
Ask a technical question →Frequently Asked Questions — Wet Scrubbers
The decision is driven by inlet dust load and whether acid gas removal is the primary objective. Venturi scrubbers excel at high-dust (>0.5 g/Nm³), high-temperature (>200°C) applications — they simultaneously quench, cool and scrub. However, their acid-gas absorption efficiency is limited (HCl: 85–95%) because contact time is short (<0.1 s). Packed-bed scrubbers achieve >99.5% HCl, >95% SO₂ and >99% HF removal because gas-liquid contact time is seconds rather than milliseconds — but they require clean inlet gas (<0.5 g/Nm³) or they foul. For most industrial applications where both particulate and acid gas must be controlled, a two-stage VS+PBS system is the engineering standard: Venturi handles the hot, dirty gas first; packed bed achieves the final acid-gas emission limit.
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View productRequest a Quote for This Equipment
Include in your enquiry:
- →Gas volumetric flow rate (Nm³/h) and operating temperature (°C)
- →Moisture content (% v/v or dew point °C)
- →Acid gas components and inlet concentrations (ppm or mg/Nm³) — HCl, SO₂, HF, NH₃, etc.
- →Inlet particulate load (g/Nm³) and particle size d50 if known
- →Required outlet emission limits (mg/Nm³) per component
- →Is liquid discharge to drain permitted on site? Is ZLD required?
- →Available utilities: water supply (m³/h, TDS), compressed air (bar), power (kV/Hz)
- →Material preference: PP, FRP, SS 316L or rubber-lined carbon steel
- →Annual operating hours and duty cycle (continuous / batch)